Laboratory Safety Manual


The Princeton University Laboratory Safety Manual is a collection of resources for individuals working in research and teaching laboratories. It includes safe work procedures, chemical safety information, laboratory equipment safety information and links to other resources, both from Princeton and other organizations. It is a web-based living document, with new items being added or revisions taking place at any time. Click here to begin.

This manual supplements your Departmental Chemical Hygiene Plan. Please review your departmental plan to familiarize yourself with the laboratory safety program in your

This manual also supplements, but does not replace, Laboratory Safety Training required for all laboratory workers and the Laboratory Safety Training Guide -- the handout given during Laboratory Safety Training.

If there are new topics that you would like to see in this manual or if you would like to contribute an article, link or other information, please contact EHS at 609-258-5294.

Table of Contents

Section 1: Laboratory Safety at Princeton University

SECTION 1: Laboratory Safety at Princeton University

Introduction (top)

Princeton University is committed to providing a safe laboratory environment for its faculty, staff, students and visitors. The goal of the University Laboratory Safety Program is to minimize the risk of injury or illness to laboratory workers by ensuring that they have the training, information, support and equipment needed to work safely in the laboratory.

The three basic elements of the Laboratory Safety Program are:

  • The departmental safety program led by the Chemical Hygiene Officer(s)
  • Laboratory safety support and training by Environmental Health and Safety
  • Instruction and oversight by an individual's supervisor or Principal Investigator

All laboratory workers, including faculty, staff and most students, are required to attend Laboratory Safety Training given by Environmental Health and Safety (EHS) staff. This training gives an overview of general laboratory safety principles, references and resources for more specific safety information, and details about several support programs, such as the hazardous waste disposal program. The training supplements instruction given by supervisors and Principal Investigators regarding safe work practices for specific chemicals and equipment.

EHS provides training, resources and consultation for a variety of laboratory safety issues, including chemical safety, laser safety, biological safety, radiation safety, electrical safety and other topics. The EHS web page offers a wide range of resources for many aspects of laboratory safety.


OSHA Laboratory Standard (top)

The Occupational Safety and Health Administration (OSHA) promulgated a regulation entitled Occupational Exposure to Hazardous Chemicals in Laboratories, otherwise known as the Laboratory Standard.

The goal of the Lab Standard is to ensure that laboratory workers are informed about the hazards of chemicals in their workplace and are protected from chemical exposures exceeding allowable levels (e.g., OSHA Permissible Exposure Limits).

All individuals who work with hazardous chemicals in science and engineering laboratories are obligated to comply with the Lab Standard. Work with chemicals outside of laboratories is covered by the OSHA Hazard Communication Standard.

For more information about how a particular department complies with the Laboratory Standard, see the Departmental Chemical Hygiene Plan.


Princeton University Policies (top)

Environmental, Health and Safety Policy

Princeton University is committed to providing a safe and healthful environment for its employees, students and visitors and managing the University in an environmentally
sensitive and responsible manner.  We further recognize an obligation to demonstrate safety and environmental leadership by maintaining the highest standards and serving as an example to our students as well as the community at large.

The University will strive to continuously improve our safety and environmental performance by adhering to the following policy objectives:

  • Developing and improving programs and procedures to assure compliance with all applicable laws and regulations
  • Ensuring that personnel are properly trained and provided with appropriate safety and emergency equipment
  • Taking appropriate action to correct hazards or conditions that endanger health, safety, or the environment
  • Considering safety and environmental factors in all operating decisions including  planning and acquisition
  • Engaging in sound reuse and recycling practices and exploring feasible opportunities to minimize the amount and toxicity of waste generated
  • Using energy efficiently throughout our operations
  • Encouraging personal accountability and emphasizing compliance with standards and conformance with University policies and best practices during employee training and in performance reviews
  • Communicating our desire to continuously improve our performance and fostering the expectation that every employee, student, and contractor on University premises will follow this policy and report any environmental, health, or safety concern to Princeton University management.
  • Monitoring our progress through periodic evaluations

Laboratory Security Policy

Safeguarding University resources from unauthorized access, misuse or removal is a duty of all faculty and staff.  In laboratories, this obligation rests primarily with the Principal Investigator; however, all laboratory personnel have a responsibility to take reasonable precautions against theft or misuse of materials, particularly those that could threaten the public.  Any extraordinary laboratory security measures should be commensurate with the potential risks and imposed in a manner that does not unreasonably hamper research.

At a minimum, the institution expects all laboratory personnel to comply with the following security procedures:

  • Question the presence of unfamiliar individuals in laboratories and report all suspicious activity immediately to Public Safety by calling 8-1000
  • After normal business hours, all laboratories must be locked when not in use

Laboratory building exterior doors are secured after normal business hours.  To minimize the likelihood of unauthorized access, all after-hours building users should:

  • Avoid providing building access to unfamiliar individuals
  • Secure doors behind them
  • Immediately report any building security problem to Public Safety at 8-3134.

Research or other activities involving the use of lab space, materials or equipment without the knowledge and approval of the responsible Principal Investigator is strictly prohibited.  Violation of this prohibition may result in disciplinary action up to and including termination.


Roles and Responsibilities (top)

Departmental Chemical Hygiene Officer

  • Establish and implement a Chemical Hygiene Plan.
  • Review and update the Chemical Hygiene Plan at least annually.
  • Investigate accidents and chemical exposures within the department.
  • Act as a liaison between the department and EHS for laboratory safety issues.
  • Maintain records of training, exposure monitoring and medical examinations.
  • Ensure laboratory workers receive chemical and procedure-specific training.
  • Review and approve use of particularly hazardous substances.
  • Approve laboratory worker's return to work following a chemical exposure requiring medical consultation.

Principal Investigators

  • Ensure laboratory workers attend general training given by EHS.
  • Ensure laboratory workers understand how to work with chemicals safely. Provide chemical and procedure-specific training, as needed.
  • Provide laboratory workers with appropriate engineering controls and personal protective equipment needed to work safely with hazardous materials. Ensure such equipment is used correctly.
  • Ensure laboratory workers complete and submit Particularly Hazardous Substance Use Approval forms and submit them for approval before using any particularly hazardous substance.
  • Review and approve work with particularly hazardous substances.

Environmental Health and Safety (EHS)

  • Conduct exposure monitoring, as needed.
  • Provide general training.
  • Audit the departmental program periodically.
  • Provide safe working guidelines for laboratory workers through the EHS web page.
  • Review the model Chemical Hygiene Plan at least annually
  • Inspect fume hoods annually
  • Provide consultation for safe work practices for hazardous chemicals
  • Conduct limited laboratory safety inspections annually
  • Develop and maintain the Laboratory Safety Manual

Laboratory Worker

Section 2: Departmental Chemical Hygiene Plans

SECTION 2: Departmental Chemical Hygiene Plans

Each science and engineering department has its own Chemical Hygiene Plan. This plan includes information about:

  • Roles and responsibilities for laboratory safety in the department
  • Chemical Hazard Identification
  • Controlling Chemical Exposures
  • Fume Hood Evaluations
  • Information and Training
  • Emergency Action Plans
  • Prior Approval for Laboratory Procedures
  • Medical Examinations and Consultations
  • Particularly Hazardous Substances
  • Laboratory Inspections and Audits
  • Department Facility Systems

To access contact information and view a particular Chemical Hygiene Plan, click on the Chemical Hygiene Plans section of the EHS website.

Section 3: Emergency Procedures

SECTION 3: Emergency Procedures

For any emergency, including fires, chemical spills, injuries, accidents, explosions, and medical emergencies, dial 911 from any University phone including blue-light phones, located in common areas throughout campus If a University phone is unavailable or inaccessible during an emergency, dial (609) 258-3333 from a cell phone.  Public Safety personnel will respond, determine whether additional assistance is needed and alert others who can help.

Each department has written an individual emergency action plan and designated an emergency coordinator and a designated assembly point. The emergency coordinator is the first point of contact for questions about the emergency procedures and the emergency action plan. The designated assembly point is where building occupants should gather in the case of a building evacuation. Make sure you are accounted for before leaving the assembly point. Rescue personnel are required to enter a building and search for individuals who are thought to still be in the building.

Be sure to familiarize yourself with the emergency action plan for your department.


Fire (top)

In the event of a fire, Public Safety should be notified immediately at 911 or (609) 258-3333 and the following actions are recommended:

1. University policy states that individuals are not required to fight fires, but that those who choose to do so may fight small, incipient stage fires (no bigger than a wastepaper basket) as long as they have been trained in the proper use of fire extinguishers.

  • If you have been trained in the use of a fire extinguisher, fight the fire from a position where you can escape, only if you are confident that you will be successful.
  • A fire contained in a small vessel can usually be suffocated by covering the vessel with a lid of some sort.

2. If your clothing catches fire, drop to the floor and roll to smother the fire. If a co-worker’s clothing catches fire, get the person to the floor and roll him or her to smother the flames. Use a safety shower immediately thereafter.

3. If the fire is large or spreading, activate the fire alarm to alert building occupants. If the fire alarm does not work, or if the building is not equipped with one, notify the building occupants verbally of the need to evacuate. If possible, shut down any equipment which may add fuel to the fire. Do not turn off any hoods in the immediate area, as they will tend to keep the area free from smoke and fumes. Close the door behind you to prevent the fire’s spread.

4. Evacuate the building and await the arrival of Public Safety. Be prepared to inform them of the exact location, details of the fire, and chemicals that are stored and used in the area.

5. Do not re-enter the building until you are told to do so by Public Safety or the municipal fire official.

There are several types of fire extinguishers available. See the advisory to determine which type is best for a particular chemical or procedure.



TigerAlert (formerly PTENS) is an emergency notification system that allows authorized Princeton officials to send news and instructions simultaneously to individuals through landline phones, cellular phones, text messaging and e-mail.  Should your building be evacuated during an emergency, this system may be used to communicate important information via cell phone or e-mail.  Faculty and staff should enter emergency contact information through the Office of Human Resources self-service website:

Graduate and undergraduate students should enter emergency contact information through the TigerHub student portal:

If you have additional questions about the TigerAlert system, e-mail your question to 


Medical Emergencies (top)

In the event of any injury or illness where assistance is needed, contact Public Safety at 911 or (609) 258-3333. If an ambulance is needed, Public Safety will arrange for one. Public Safety staff can transport individuals with minor injuries to University Health Services at McCosh or Princeton Medical Center, as appropriate.

First Aid Kits

According to the Princeton University Policy on First Aid, first aid kits maintained by University departments and offices must:

  • be kept in sanitary condition;
  • be limited to simple household supplies such as band-aids and sterile gauze pads; and
  • include the following personal protective equipment:
  • at least one pair of large size examination or laboratory gloves
  • an airway resuscitator, such as the "pocket mask", for use in mouth-to-mouth resuscitation
  • a spill kit containing an appropriate disinfectant and other cleanup and disposal materials for handling spills of blood, vomitus, or other body fluids.

The supplies listed above have been approved by the University Employee Health group as required by OSHA regulations. No other first aid supplies are authorized unless arranged through Employee Health. Treatment requiring more elaborate supplies should be sought at McCosh Health Center or Princeton Medical Center.

All work-related injuries or illnesses must be reported to supervisors and the Chemical Hygiene Officer.


Chemical Exposures (top)

The following procedures should be followed in the event of chemical exposure. In all cases, the incident should be reported to your laboratory manager, supervisor or principal investigator, regardless of severity. Consult your department manager to determine whether or not a First Report of Accidental Injury or Occupational Illness form should be completed.

Chemicals on Skin or Clothing

  1. Immediately flush with water for no less than 15 minutes (except for Hydrofluoric Acid, Flammable Solids or >10% Phenol). For larger spills, the safety shower should be used.
  2. While rinsing, quickly remove all contaminated clothing or jewelry. Seconds count. Do not waste time because of modesty.
  3. Use caution when removing pullover shirts or sweaters to prevent contamination of the eyes.
  4. Check the Safety Data Sheet (SDS) to determine if any delayed effects should be expected.
  5. Discard contaminated clothing or launder them separately from other clothing. Leather garments or accessories cannot be decontaminated and should be discarded.

Do not use solvents to wash skin. They remove the natural protective oils from the skin and can cause irritation and inflammation. In some cases, washing with a solvent may facilitate absorption of a toxic chemical.

For flammable solids on skin, first brush off as much of the solid as possible, then proceed as described above.

For hydrofluoric acid, rinse with water for 5 minutes. Apply 2.5% calcium gluconate gel, a tube for your lab can be obtained prior through EHS.  If not readily available, continue rinsing for 15 minutes. In all cases, seek medical attention immediately. Go immediately to University Health Services at McCosh or Princeton Medical Center.

For phenol concentrations more than 10%, flush with water for 15 minutes or until the affected area turns from white to pink. Apply a solution of 400 molecular weight polyethylene glycol, if available. Do not use ethanol.  Proceed as described above.

Chemicals in Eyes

  1. Immediately flush eye(s) with water for at least fifteen minutes. The eyes must be forcibly held open to wash, and the eyeballs must be rotated so all surface area is rinsed. The use of an eye wash fountain is desirable so hands are free to hold the eyes open. If an eyewash is not available, pour water on the eye, rinsing from the nose outward to avoid contamination of the unaffected eye.
  2. Remove contact lenses while rinsing. Do not lose time removing contact lenses before rinsing. Do not attempt to rinse and reinsert contact lenses.
  3. Seek medical attention regardless of the severity or apparent lack of severity.  If an ambulance or transportation to McCosh Health Center is needed, contact Public Safety at 911 or (609) 258-3333. Explain carefully what chemicals were involved.  If easily accessible, bring an MSDS.

Chemical Inhalation

  1. Close containers, open windows or otherwise increase ventilation, and move to fresh air.
  2. If symptoms, such as headaches, nose or throat irritation, dizziness, or drowsiness persist, seek medical attention by calling Public Safety or going to University Health Services at McCosh. Explain carefully what chemicals were involved.
  3. Review the MSDS to determine what health effects are expected, including delayed effects.

Accidental Ingestion of Chemicals

  1. Immediately go to University Health Services at McCosh or contact the Poison Control Center at 800-962-1253 for instructions.
  2. Do not induce vomiting unless directed to do so by a health care provider.

Accidental Injection of Chemicals

Wash the area with soap and water and seek medical attention, if necessary.


Emergency Information Posters (top)

The purpose of the Emergency Information Poster is to provide an easily recognizable and consistent means of displaying essential information about the status and contents of laboratories and facilities, primarily for the benefit of persons attempting to cope with an explosion, fire, natural disaster, or other emergency. Such information is important for the safety of emergency personnel and is often of considerable value in evaluating and dealing with the emergency.

The poster is to be posted on the outside of doors leading into areas where there are potential hazards and an electronic copy is retained by Public Safety. If you have questions contact Joan Hutlzy (8-6251). EHS sends a semi-annual reminder to all Departmental Safety Managers to update the information on the posters.

Obtaining Posters

A poster pre-printed with the building name, room number and room diagram may be obtained from Joan Hutzly. You may also download a blank poster in MS Word format, however it is preferable to use the pre-printed poster. A sample poster is provided below. Follow the instructions for completing the poster.

Laser Emergency Information


The poster calls for the following information:

  1. The home and office phone numbers of persons responsible for and familiar with the laboratory operations.
  2. A floor plan of the room, with depictions of appropriate furniture, fume hoods, lab benches, storage cabinets.
  3. Location of principal storage areas for hazardous materials in the room as well as recommended personal protective equipment, following guidelines given in the Emergency Information Poster instructions.
  4. Specific emergency instructions or warnings, where necessary.


Reporting Accidents and Injuries (top)

All accidents, injuries, or near-misses should be reported to your supervisor or Principal Investigator.

If a laboratory worker believes that he or she has been over-exposed to a chemical, the worker or supervisor should contact EHS at 258-5294, regardless of whether or not signs or symptoms are noted. EHS will contact the individual and lab manager to conduct an incident investigation.

Princeton University EHS encourages a culture of reporting all incidents and near misses. Incident investigations are conducted to work towards safer working environments and practices. These investigations are not to assign blame or responsibility for an accident.

If an individual calls from home to report a work-related injury or illness, the information necessary to complete the first report should be obtained at that time. Individuals who are unable to travel to University Health Services at McCosh should be advised to call Employee Health (8-5035) for referrals to approved medical care providers.

Section 4: Chemical and Hazard Identification

Section 4: Chemical and Hazard Identification

Chemical manufacturers are required to perform an assessment of the physical and health hazards of the chemicals they produce. This information must be made available in two places: the chemical label and the material safety data sheet (MSDS). Thus, the information found on the original container label and the MSDS may provide a great deal of information about the identity of the chemical constituents and their health and physical hazards.


Labels (top)

The manufacturer’s label should be kept intact. Do not intentionally deface or obscure the label or the hazard warnings until the container has been completely emptied. When a chemical is transferred from the original container into a secondary container for storage, the new container should be labeled with the name of the product, the chemical constituents and the primary hazard warnings.


Safety Data Sheets (top)

All chemical manufacturers or distributors are required to conduct a hazard evaluation of their products and include the information on a safety data sheet (SDS). The manufacturer or distributor is required to provide an SDS with the initial shipment of their products. Any SDS received by the laboratory must be maintained in a central location in the laboratory or the department. The Chemical Hygiene Plan outlines what to do with SDS received by a particular laboratory.

SDSs are sometimes difficult to interpret. For more information about understanding and using an SDS, see the Guide to Understanding SDS Information.

If an SDS is not on hand, check the EHS web page for connections to on-line sources of SDSs. If the SDS cannot be found, contact the manufacturer or distributor at the number listed on the container label and request an SDS. If the manufacturer does not provide one within a few days, contact EHS for assistance.


On-line Chemical Information Resources (top)

The SDS section of the EHS web page has a number of pointers to on-line collections of SDS and other chemical information sources. The Laboratory Safety page has even more pointers to chemical and laboratory safety information. 


Other Chemical Information Resources (top)

A number of books with chemical safety information are available through EHS or the University Library. The following is a partial listing – titles available through the University Library are identified with an asterisk (*):

Armour, Margaret-Ann, Hazardous Laboratory Chemical Disposal Guide, Lewis Publishers, NY, 1996

*Bretherick, I., Handbook of Reactive Chemical Hazards, 4th ed., CRC Press, 1990.

 British Cryogenic Council, Cryogenics Safety Manual, 3rd ed., 1991.

*Clayton, George and F. Clayton, editors, Patty’s Industrial Hygiene and Toxicology, Wiley, Interscience, 1991.

*Compressed Gas Association, Inc., Handbook of Compressed Gases, 3rd ed., VanNostrand Reinhold Company, New York, 1990.

Forsberg, Krister and Lawrence Keith, Chemical Protective Clothing Performance Index, Wiley and Sons, NY, 1999

*Furr, A. Keith, Handbook of Laboratory Safety, 5th ed., The Chemical Rubber Company, 2000.

*Gosselin,et al, Clinical Toxicology of Commercial Products, 5th ed., Williams & Wilkins, 1984.

* Lewis, Richard J., The Condensed Chemical Dictionary, 12th ed., Van Nostrand Reinhold Company, 1993.

*Lewis, Richard J., Dangerous Properties of Industrial Materials, 8th ed., Litton Educational Publishing Inc., 1992.

Meyer, Eugene, Chemistry of Hazardous Materials, Prentice Hall, Englewood Cliffs, NJ, 1977

*National Academy of Sciences, Prudent Practices for Handling Hazardous Chemicals in Laboratories, 1995.

*National Institute of Occupational Safety and Health, Registry of Toxic Effects of Chemical Substances, (published annually).

*National Research Council, Prudent Practices in the Laboratory, National Academy Press, Washington, DC 1995

Office of Technology Assessment Task Force, Reproductive Health

Hazards in the Workplace, Science Information Resource Center, Philadephia, PA 1988

Patnaik, Pradyot, Comprehensive Guide to Hazardous Properties of Chemical Substances, Wiley and Sons, NY, 1999

Pohanish, Richard, Rapid Guide to Chemical Incompatibilities, Wiley & Sons, NY, 1997

*U.S. Department of Health and Human Services, Occupational Health Guidelines for Chemical Hazards,            

Stull, Jeffrey, PPE Made Easy, Government Institutes, Rockville, MD, 1998

Section 5: Health Hazards of Chemicals

SECTION 5: Health Hazards of Chemicals


Introduction (top)

The decisions you make concerning the use of chemicals in the laboratory should be based on an objective analysis of the hazards, rather than merely the perception of the risks involved. Once this has been accomplished, a reasonable means of controlling the hazards through experimental protocol, work practices, ventilation, use of protective clothing, etc., can be determined.

In order to assess the hazards of a particular chemical, both the physical and health hazards of the chemical must be considered.

Before using any chemical, the safety data sheet (SDS) or other appropriate resource should be reviewed to determine what conditions of use might pose a hazard. Accidents with hazardous chemicals can happen quickly and may be quite severe. The key to prevention of these accidents is awareness. Once the hazards are known, the risk of an accident may be reduced significantly by using safe work practices.


Basic Toxicology (top)

The health effects of hazardous chemicals are often less clear than the physical hazards. Data on the health effects of chemical exposure, especially from chronic exposure, are often incomplete. When discussing the health effects of chemicals, two terms are often used interchangeably - toxicity and hazard. However, the actual meanings of these words are quite different. Toxicity is an inherent property of a material, similar to its physical constants. It is the ability of a chemical substance to cause an undesirable effect in a biological system. Hazard is the likelihood that a material will exert its toxic effects under the conditions of use. Thus, with proper handling, highly toxic chemicals can be used safely. Conversely, less toxic chemicals can be extremely hazardous if handled improperly.


The actual health risk of a chemical is a function of the toxicity and the actual exposure. No matter how toxic the material may be, there is little risk involved unless it enters the body. An assessment of the toxicity of the chemicals and the possible routes of entry will help determine what protective measures should be taken.


Routes of Entry (top)

eyeLungsStomachhypodermic needle

Skin and Eye Contact

The simplest way for chemicals to enter the body is through direct contact with the skin or eyes. Skin contact with a chemical may result in a local reaction, such as a burn or rash, or absorption into the bloodstream. Absorption into the bloodstream may then allow the chemical to cause toxic effects on other parts of the body. The MSDS usually includes information regarding whether or not skin absorption is a significant route of exposure.

The absorption of a chemical through intact skin is influenced by the health of the skin and the properties of the chemical. Skin that is dry or cracked or has lacerations offers less resistance. Fat-soluble substances, such as many organic solvents, can easily penetrate skin and, in some instances, can alter the skin’s ability to resist absorption of other substances.

Wear gloves and other protective clothing to minimize skin exposure. See Personal Protective Equipment for more information. Symptoms of skin exposure include dry, whitened skin, redness and swelling, rashes or blisters, and itching. In the event of chemical contact on skin, rinse the affected area with water for at least 15 minutes, removing clothing while rinsing, if necessary. Seek medical attention if symptoms persist.

Avoid use of solvents for washing skin. They remove the natural protective oils from the skin and can cause irritation and inflammation. In some cases, washing with a solvent may facilitate absorption of a toxic chemical.

Chemical contact with eyes can be particularly dangerous, resulting in painful injury or loss of sight. Wearing safety goggles or a face shield can reduce the risk of eye contact. Eyes that have been in contact with chemicals should be rinsed immediately with water continuously for at least 15 minutes. Contact lenses should be removed while rinsing—do not delay rinsing to remove the lenses. Medical attention is necessary if symptoms persist.


The respiratory tract is the most common route of entry for gases, vapors, particles, and aerosols (smoke, mists and and fumes). These materials may be transported into the lungs and exert localized effects, or be absorbed into the bloodstream. Factors that influence the absorption of these materials may include the vapor pressure of the material, solubility, particle size, its concentration in the inhaled air, and the chemical properties of the material. The vapor pressure is an indicator of how quickly a substance evaporates into the air and how high the concentration in air can become – higher concentrations in air cause greater exposure in the lungs and greater absorption in the bloodstream.

Most chemicals have an odor that is perceptible at a certain concentration, referred to as the odor threshold; however, there is no relationship between odor and toxicity. There is considerable individual variability in the perception of odor. Olfactory fatigue may occur when exposed to high concentrations or after prolonged exposure to some substances. This may cause the odor to seem to diminish or disappear, while the danger of overexposure remains.

Symptoms of over-exposure may include headaches, increased mucus production, and eye, nose and throat irritation. Narcotic effects, including confusion, dizziness, drowsiness, or collapse, may result from exposure to some substances, particularly many solvents. In the event of exposure, close containers or otherwise increase ventilation, and move to fresh air. If symptoms persist, seek medical attention.

Volatile hazardous materials should be used in a well-ventilated area, preferably a fume hood, to reduce the potential of exposure. Occasionally, ventilation may not be adequate and a fume hood may not be practical, necessitating the use of a respirator. The Occupational Safety and Health Administration Respiratory Protection Standard regulates the use of respirators; thus, use of a respirator is subject to prior review by EHS according to University policy. See Personal Protective Equipment for more information.


The gastrointestinal tract is another possible route of entry for toxic substances. Although direct ingestion of a laboratory chemical is unlikely, exposure may occur as a result of ingesting contaminated food or beverages, touching the mouth with contaminated fingers, or swallowing inhaled particles which have been cleared from the respiratory system. The possibility of exposure by this route may be reduced by not eating, drinking, smoking, or storing food in the laboratory, and by washing hands thoroughly after working with chemicals, even when gloves were worn.

Direct ingestion may occur as a result of the outdated and dangerous practice of mouth pipetting. In the event of accidental ingestion, immediately go to McCosh Health Center or contact the Poison Control Center, at 800-962-1253 for instructions. Do not induce vomiting unless directed to do so by a health care provider.


The final possible route of exposure to chemicals is by injection. Injection effectively bypasses the protection provided by intact skin and provides direct access to the bloodstream, thus, to internal organ systems. Injection may occur through mishaps with syringe needles, when handling animals, or through accidents with pipettes, broken glassware or other sharp objects that have been contaminated with toxic substances.

If injection has occurred, wash the area with soap and water and seek medical attention, if necessary. Cautious use of any sharp object is always important. Substituting cannulas for syringes and wearing gloves may also reduce the possibility of injection.


Toxic Effects of Chemical Exposure (top)

How a chemical exposure affects a person depends on many factors. The dose is the amount of a chemical that actually enters the body. The actual dose that a person receives depends on the concentration of the chemical and the frequency and duration of the exposure. The sum of all routes of exposure must be considered when determining the dose.

In addition to the dose, the outcome of exposure is determined by (1) the way the chemical enters the body, (2) the physical properties of the chemical, and (3) the susceptibility of the individual receiving the dose.

Toxic Effects of Chemicals

The toxic effects of a chemical may be local or systemic. Local injuries involve the area of the body in contact with the chemical and are typically caused by reactive or corrosive chemicals, such as strong acids, alkalis or oxidizing agents. Systemic injuries involve tissues or organs unrelated to or removed from the contact site when toxins have been transported through the bloodstream. For example, methanol that has been ingested may cause blindness, while a significant skin exposure to nitrobenzene may effect the central nervous system.

Certain chemicals may affect a target organ. For example, lead primarily affects the central nervous system, kidney and red blood cells; isocyanates may induce an allergic reaction (immune system); and chloroform may cause tumors in the liver and kidneys.

It is important to distinguish between acute and chronic exposure and toxicity. Acute toxicity results from a single, short exposure. Effects usually appear quickly and are often reversible. Chronic toxicity results from repeated exposure over a long period of time. Effects are usually delayed and gradual, and may be irreversible. For example, the acute effect of alcohol exposure (ingestion) is intoxication, while the chronic effect is cirrhosis of the liver. Acute and chronic effects are distinguished in the MSDS, usually with more information about acute exposures than chronic.

Relatively few chemicals have been evaluated for chronic effects, given the complexity of that type of study. Chronic exposure may have very different effects than acute exposure. Usually, studies of chronic exposure evaluate its cancer causing potential or other long-term health problems.

Evaluating Toxicity Data

Most estimates of human toxicity are based on animal studies, which may or may not relate to human toxicity. In most animal studies, the effect measured is usually death. This measure of toxicity is often expressed as an LD50 (lethal dose 50) – the dose required to kill 50% of the test population. The LD50 is usually measured in milligrams of the material per kilogram of body weight of the test animal. The concentration in air that kills half of the population is the LC50.

To estimate a lethal dose for a human based on animal tests, the LD50 must be multiplied by the weight of an average person. Using this method, it is evident that just a few drops of a highly toxic substance, such as dioxin, may be lethal, while much larger quantities of a slightly toxic substance, such as acetone, would be necessary for the same effect.

Susceptibility of Individuals

Factors that influence the susceptibility of an individual to the effects of toxic substances include nutritional habits, physical condition, obesity, medical conditions, drinking and smoking, and pregnancy. Due to individual variation and uncertainties in estimating human health hazards, it is difficult to determine a dose of a chemical that is totally risk-free.

Regular exposure to some substances can lead to the development of an allergic rash, breathing difficulty, or other reactions. This phenomenon is referred to as sensitization. Over time, these effects may occur with exposure to smaller and smaller amounts of the chemical, but will disappear soon after the exposure stops. For reasons not fully understood, not everyone exposed to a sensitizer will experience this reaction. Examples of sensitizers include epoxy resins, nickel salts, isocyanates and formaldehyde.

Particularly Hazardous Substances

The OSHA Laboratory Standard defines a particularly hazardous substance as "select carcinogens", reproductive toxins, and substances that have a high degree of acute toxicity. Further information about working with Particularly Hazardous Substances is outlined in Particularly Hazardous Substances.

Where To Find Toxicity Information

Toxicity information may be found in Material Safety Data Sheets, under the "Health Hazard Data" section, on product labels, in the Registry of Toxic Effects of Chemical Substances (RTECS), or in many other sources listed in the SDS page.


Chemical Exposure Determination (top)

OSHA establishes exposure limits for several hundred substances. Laboratory workers must not be exposed to substances in excess of the permissible exposure limits (PEL) specified in OSHA Subpart Z, Toxic and Hazardous Substances. PELs refer to airborne concentrations of substances averaged over an eight-hour day. Some substances also have "action levels" below the PEL requiring certain actions such as medical surveillance or routine air sampling.

The MSDS for a particular substance indicates whether any of the chemicals are regulated through OSHA and, if so, the permissible exposure limit(s) for the regulated chemical(s). This information is also available in the OSHA Table Z list of regulated chemicals.

Exposure Monitoring

Exposure monitoring must be conducted if there is reason to believe that exposure levels for a particular substance may routinely exceed either the action level or the PEL. EHS and the principal investigator or supervisor may use professional judgment, based on the information available about the hazards of the substance and the available control measures, to determine whether exposure monitoring must be conducted.

When necessary, exposure monitoring is conducted by EHS according to established industrial hygiene practices. Results of the monitoring are made available to the individual monitored, his or her supervisor, and the departmental Chemical Hygiene Officer within 15 working days of the receipt of analytical results.

Based on the monitoring results, periodic air sampling may be scheduled at the discretion of EHS, in accordance with applicable federal, state and local regulations.

EHS maintains records of all exposure monitoring results. Departmental Chemical Hygiene Officers should keep records of monitoring conducted for their department operations.

Section 6A: Controlling Chemical Exposures

SECTION 6A: Controlling Chemical Exposures


General Principles (top)

There are three general methods for controlling one's exposure to hazardous substances:

  • Engineering Controls
  • Work Practices and Administrative Controls
  • Personal Protective Equipment

In the laboratory, these methods or a combination of them can be used to keep exposure below permissible exposure limits.

Engineering Controls

Engineering controls include the following:

  • Substitution of a less toxic material
  • Change in process to minimize contact with hazardous chemicals
  • Isolation or enclosure of a process or operation
  • Use of wet methods to reduce generation of dusts or other particulates
  • General dilution ventilation
  • Local exhaust, including the use of fume hoods

The use of engineering controls is the preferred method for reducing worker exposure to hazardous chemicals, but with the exception of chemical fume hoods, may not be feasible in the laboratory.

Work Practice and Administrative Controls

Using good laboratory work practices, such as those outlined in this manual, help to reduce the risk of exposure to chemicals.

Administrative controls involve rotating job assignments and adjusting work schedules so that workers are not overexposed to a chemical. Given the nature of work in a research laboratory, administrative controls are not usually a realistic approach to controlling exposure.

Personal Protective Equipment

When engineering controls are not sufficient to minimize exposure, personal protective equipment, including gloves, eye protection, respirators and other protective clothing should be used. See Personal Protective Equipment for more information.

Section 6B: Lab Ventilation

SECTION 6B: Fume Hoods and Laboratory Ventilation


Fume Hoods and Laboratory Ventilation (top)

One of the primary safety devices in a laboratory is a chemical fume hood. A well-designed hood, when properly installed and maintained, can offer a substantial degree of protection to the user, provided that it is used appropriately and its limitations are understood.

This section covers a number of topics aimed at helping laboratory workers understand the limitations and proper work practices for using fume hoods and other local ventilation devices safely.

There are basically two types of fume hoods at Princeton, they are:
Constant volume – where the exhaust flowrate or quantity of air pulled through the hood is constant. Therefore, when the sash is lowered and the cross-sectional area of the hood opening decreases, the velocity of airflow (face velocity) through the hood increases proportionally. Thus, higher face velocities can be obtained by lowering the sash.

And variable air volume (VAV) - where the exhaust flowrate or quantity of air pulled through the hood varies as the sash is adjust in order to maintain a set face velocity. Therefore, when the sash is lowered and the cross-sectional area of the hood opening decreases, the velocity of airflow (face velocity) through the hood stays the same while less total air volume is exhausted.


How a Fume Hood Works (top)

Fume Hood Plans

A fume hood is a ventilated enclosure in which gases, vapors and fumes are contained. An exhaust fan situated on the top of the laboratory building pulls air and airborne contaminants in the hood through ductwork connected to the hood and exhausts them to the atmosphere.

The typical fume hood found in Princeton University laboratories is equipped with a movable front sash and an interior baffle. Depending on its design, the sash may move vertically, horizontally or a combination of the two and provides some protection to the hood user by acting as a barrier between the worker and the experiment.

The slots and baffles direct the air being exhausted. In many hoods, they may be adjusted to allow the most even flow. It is important that the baffles are not closed or blocked since this blocks the exhaust path.

The airfoil or beveled frame around the hood face allows more even airflow into the hood by avoiding sharp curves that can create turbulence.

In most hood installations, the exhaust flowrate or quantity of air pulled through the hood is constant. Therefore, when the sash is lowered and the cross-sectional area of the hood opening decreases, the velocity of airflow (face velocity) through the hood increases proportionally. Thus, higher face velocities can be obtained by lowering the sash.

Using Chemical Fume Hoods (top)

A fume hood is used to control exposure of the hood user and lab occupants to hazardous or odorous chemicals and prevent their release into the laboratory. A secondary purpose is to limit the effects of a spill by partially enclosing the work area and drawing air into the enclosure by means of an exhaust fan. This inward flow of air creates a dynamic barrier that minimizes the movement of material out of the hood and into the lab.

In a well-designed, properly functioning fume hood, only about 0.0001% to 0.001% of the material released into the air within the hood actually escapes from the hood and enters the laboratory.

When is a Fume Hood Necessary?

The determination that a fume hood is necessary for a particular experiment should be based on a hazard analysis of the planned work. Such an analysis should include:

  • A review of the physical characteristics, quantity and toxicity of the materials to be used;
  • The experimental procedure;
  • The volatility of the materials present during the experiment;
  • The probability of their release;
  • The number and sophistication of manipulations; and
  • The skill and expertise of the individual performing the work.


Good Work Practices (top)

The level of protection provided by a fume hood is affected by the manner in which the fume hood is used. No fume hood, however well designed, can provide adequate containment unless good laboratory practices are used, as follow:

  1. Adequate planning and preparation are key.The hood user should know the Standard Operating Configuration (SOC) of the hood and should design experiments so that the SOC can be maintained whenever hazardous materials might be released. The SOC refers to the position of the sash. A schematic drawing of the SOC is displayed on the front of each chemical fume hood.
  2. Before using the hood, the user should check the hood survey sticker to determine where the sash should be positioned for optimum containment for that particular unit.
  3. The hood user should also check the magnehelic gauge or other hood performance indicator and compare its reading to the reading indicated on the hood survey sticker. If the reading differs significantly (15% or more for a magnehelic gauge) from that on the sticker, the hood may not be operating properly.

Items contaminated with odorous or hazardous materials should be removed from the hood only after decontamination or if placed in a closed outer container to avoid releasing contaminants into the laboratory air.

When using cylinders containing highly toxic or extremely odorous gases, obtain only the minimal practical quantity. Consider using a flow-restricting orifice to limit the rate of release in the event of equipment failure. In some circumstances, exhaust system control devices or emission monitoring in the exhaust stack may be appropriate.

To optimize the performance of the fume hood, follow the practices listed below:

  • Mark a line with tape 6 inches behind the sash and keep all chemicals and equipment behind that line during experiments. This will help to keep materials from escaping the hood when disturbances like air currents from people walking past the hood, etc., interfere with airflow at the face of the hood.


Fume Hood Placement
Images from Kewaunee Fume Hoods

Bad placement of materials.

Good placement of materials.

Best placement of materials.

    • Provide catch basins for containers that could break or spill, to minimize the spread of spilled liquids.
    • Keep the sash completely lowered any time an experiment is in progress and the hood is unattended. Note: Lowering the sash not only provides additional personal protection, but it also results in significant energy conservation.
    • Never use a hood to control exposure to hazardous substances without first verifying that it is operating properly.
    • Visually inspect the baffles (openings at the top and rear of the hood) to be sure that the slots are open and unobstructed.  For optimum performance, adjust the baffles when working with high temperature equipment and/or heavy gases or vapors.  See figure below for suggested baffle positions.

Slot all large

Normal baffle position - all slots are open.

Slot position for high temperature equipment, such as hot plates. 

Lower slot is minimized since heated vapors tend to rise.

Slot position for heavy gases and vapors. 

Upper slot is minimized.

Images from Kewaunee Fume Hoods



  • Do not block slots. If large equipment must be placed in the hood, put it on blocks to raise it approximately 2 inches above the surface so that air may pass beneath it.  See figure below.

Large Equipment
Images from Kewaunee Fume Hoods

Poor placement of large equipment

Good placement of large equipment

    • Place large or bulky equipment near the rear of the fume hood. Large items near the face of the hood may cause excessive air turbulence and variations in face velocity.
    • Do not use the hood as a storage device. Keep only the materials necessary for the experiment inside of the hood. If chemicals must be stored in the hood for a period of time, install shelves on the sides of the hood, away from the baffles. See Use of Hood as a Storage Device for more information.
    • Keep the hood sash clean and clear.
    • Check area around the hood for sources of cross drafts, such as open windows, supply air grilles, fans and doors. Cross drafts may cause turbulence that can allow leaks from the hood into the lab.
    • Extend only hands and arms into the hood and avoid leaning against it. If the hood user stands up against the face of the hood, air currents produced by turbulent airflow may transport contaminants into the experimenter's breathing zone.
    • Clean all chemical residues from the hood chamber after each use.
    • All electrical devices should be connected outside the hood to avoid electrical arcing that can ignite a flammable or reactive chemical.
    • DO NOT USE A HOOD FOR ANY FUNCTION FOR WHICH IT WAS NOT INTENDED. Certain chemicals or reactions require specially constructed hoods. Examples are perchloric acid or high pressure reactions. Most special use hoods are labeled with the uses for which they are designed. See Common Misuses of Fume Hoods for more information.


Common Misuses and Limitations (top)

Used appropriately, a fume hood can be a very effective device for containment hazardous materials, as well as providing some protection from splashes and minor explosions. Even so, the average fume hood does have several limitations.

  • Particulates: A fume hood is not designed to contain high velocity releases of particulate contaminants unless the sash is fully closed.
  • Pressurized systems: Gases or vapors escaping from pressurized systems may move at sufficient velocity to escape from the fume hood.
  • Explosions: The hood is not capable of containing explosions, even when the sash is fully closed. If an explosion hazard exists, the user should provide anchored barriers, shields or enclosures of sufficient strength to deflect or contain it. Such barriers can significantly affect the airflow in the hood.
  • Perchloric Acid: A conventional fume hood must not be used for perchloric acid. Perchloric acid vapors can settle on ductwork, resulting in the deposition of perchlorate crystals. Perchlorates can accumulate on surfaces and have been known to detonate on contact, causing serious injury to researchers and maintenance personnel. Specialized perchloric acid hoods, made of stainless steel and equipped with a washdown system must be used for such work. 
  • Air Foil Sills: Many fume hoods are equipped with flat or rounded sills or air foils which direct the flow of air smoothly across the work surface. Sills should not be removed or modified by the hood user. Objects should never be placed on these sills. Materials released from containers placed on the sills may not be adequately captured. In addition, an object on the sill may prevent the quick and complete closure of the sash in an emergency.
  • Spill Containment Lips: Most modern fume hoods have recessed work surfaces or spill containment lips to help contain minor liquid spills. In many cases, these lips are several inches wide. Containers of liquids should not be placed on the hood lip.
  • Horizontal Sliding Sashes: The hood user should never remove sliding sashes. Horizontal sash hoods are designed and balanced with no more than half the face open at any time. Removal of sashes may reduce the face velocity below acceptable levels.
  • Tubing for Exhaust: Tubing is frequently used to channel exhaust to the hood from equipment located some distance away. This is not an effective control method.
  • Connections to the Exhaust System: Occasionally, a researcher may need local exhaust ventilation other than that provided by an existing fume hood. A new device may not be connected to an existing fume hood without the explicit approval of the department's facilities manager or Special Facilities supervisor. Adding devices to even the simplest exhaust system without adequate evaluation and adjustment will usually result in decreased performance of the existing hood and/or inadequate performance of the additional device.
  • Microorganisms: Work involving harmful microorganisms should be done in a biosafety cabinet, rather than a chemical fume hood. See the Biosafety Manual for more information.
  • Highly Hazardous Substances: A well designed fume hood will contain 99.999 – 99.9999% of the contaminants released within it when used properly. When working with highly dangerous substances needing more containment than a fume hood offers, consider using a glove box.
  • Pollution Control: An unfiltered fume hood is not a pollution control device. All contaminants that are removed by the ventilating system are released directly into the atmosphere. Apparatus used in hoods should be fitted with condensers, traps or scrubbers to contain and collect waste solvents or toxic vapors or dusts. 
  • Waste Disposal: A fume hood should not be used for waste disposal. It is a violation of environmental regulations to intentionally send waste up the hood stack. As described above, the hood is not a pollution control device.

The Fume Hood as a Storage Device

Fume hoods are designed specifically to provide ventilation for the protection of lab occupants during chemical manipulations. The airflow they provide is greatly in excess of that needed for storage of closed containers of even the most toxic of volatile materials. Storing materials in this way is, therefore, a misuse of an expensive piece of equipment.

In general, the storage of chemicals in fume hoods is strongly discouraged. See Flammable Materials for more information about proper storage of flammable, toxic, or odorous chemicals.

The realities of available space and equipment in some laboratories may make it difficult or impossible to completely prohibit the use of hood workspaces for storage. In such a case, the following general policy is recommended:

Hoods Actively in Use for Experimentation

Storage of materials should be minimized or eliminated altogether. Materials stored in the hood can adversely affect the containment provided. In addition, the hood is frequently the focus of the most hazardous activities conducted in the laboratory. The presence of stored flammable or volatile, highly toxic materials can only exacerbate the problems resulting from an explosion or fire in the hood. Even if they are not directly involved in such an event, attempts to control or extinguish a fire may result in the spilling of stored materials.

Hoods Not in Active Use

Materials requiring ventilated storage (e.g., volatile and highly toxic, or odorous substances) may be stored in a hood if they are properly segregated and the hood is posted to prohibit its use for experimental work.


Hood Performance Indicators (top)

All fume hoods at Princeton University are equipped with some type of continuous airflow monitoring device, either in the form of a magnehelic gauge, a color coded flow indicator or a face velocity monitor. Some are equipped with alarms.

Each hood also has a survey sticker with important information to help determine whether the particular hood is functioning properly and is appropriate for the work to be performed.

Continuous Monitoring Devices

Static Pressure Gauge (Magnehelic)

Pressure Gauge

Most fume hoods on campus are equipped with static pressure gauges that measure the difference in static pressure across an orifice in the duct, or between the laboratory and the fume hood exhaust duct. Most of the devices are aneroid pressure gauges, such as magnehelics, that are mounted on the front of the hood above the sash.

The gauge is a flow rate indicator with a scale that reads in units of pressure, rather than velocity. Changes in the magnehelic reading are not linearly proportional to changes in face velocity; therefore it should only be used as an index of hood performance.

The magnehelic gauge reading at the time of the most recent hood survey is shown on each fume hood evaluation sticker. A difference of 15% or more in the magnehelic reading from that shown on the sticker is an indication that the flow rate in the duct, and thus the face velocity, may have changed significantly since the last survey. If the user notices such a change, or has any other reason to suspect that the hood is not operating properly, contact EHS at 258-5294 for a re-survey of the hood.

Color Coded Flow Indicators

Some hoods are equipped with FlowSafe devices, rather than magnehelic gauges. This device constantly measures the face velocity of the hood and, using a needle that either points to green (for good) or red, indicates whether or not the hood is functioning properly.

Flow Monitor

Face Velocity Monitors

Some of the newer hoods have constant face velocity measuring devices. An LED readout of the face velocity is found on the device on the top corner of the hood opening. The readout indicates the actual face velocity of the hood, and should be a negative number, to reflect that the direction of flow is negative, into the hood, rather than positive, out of the hood.

Face Velocity Monitor

Alarm-Equipped Hoods

Many hoods in areas of Frick, Moffett and E-Quad are equipped with sash position alarms. These hoods are designed to operate with the hood sash lowered to approximately 20 inches above the base of the hood, in order to conserve energy by exhausting air at a lower flow rate than would otherwise be necessary.

When the sash is raised above 20 inches, a buzzer will sound and a red light will begin flashing, alerting the hood user and other laboratory occupants that the hood face velocity is now likely to be below 100 feet per minute. In the event that the sash must be raised above 20 inches, such as when large equipment must be installed or removed, the buzzer can be turned off manually, but the light will continue flashing until the sash is lowered below the 20 inch mark.

All chemical manipulations performed in an alarm equipped hood should be done with the sash opening at 20 inches or less.

Hood Survey Sticker

Every chemical fume hood on campus should have a survey sticker affixed to the front of the hood in a conspicuous location. The sticker contains basic information about hood performance as of the most recent survey and should be consulted each time the hood is used.

Hood StickerThe EHS Hood Number is a unique identifier for the particular hood. Refer to this number when discussing problems with a particular hood.

The Inspection Sticker is aligned on the hood so the arrow is in the proper location for the maximum safe sash position.

The Flow Monitor Reading is the reading of the magnehelic gauge or other continuous monitoring device at the time of the survey. Where the hood has two possible exhaust rates, as is the case for some hoods in Frick, the reading corresponding to each rate may be indicated as, for example, 0.31/0.42.

The Inspected on date is the date of the last hood survey. Hoods that have not been surveyed within the past year should not be used until tested by EHS.

The By line gives the name of the EHS technician who surveyed the hood.

If hood performance is judged to be unsuitable for use with hazardous chemicals, a sticker with this information is placed on the hood instead of the survey sticker.
Caution Sticker

Do not use a hood that has no survey sticker. If a survey is needed, call EHS at 258-5294.


Evaluation and Maintenance Program (top)

Hood Surveys

EHS surveys each fume hood annually. The face velocity of the fume hood is measured with the sash in the Standard Operating Configuration (SOC). The inspection sticker is positioned on the hood so the arrow is in the proper location for the maximum safe sash position. The reading of the continuous monitoring device is recorded on the hood sticker.

After each performance survey, a written report of the results is furnished to the individual responsible for the hood (e.g., the Principal Investigator or laboratory manager), the Chemical Hygiene Officer for the department, and the Special Facilities staff for the laboratory building.

When Problems are Noted

There are several factors that can affect the performance of the hood, resulting in low face velocity or turbulent airflow. These include mechanical problems or exhaust slots blocked by large objects or excessive storage.

If a problem is found during the hood survey, a written notice will be provided on-site to the laboratory or taped to the sash of the fume hood. If the problem requires the need for work practice changes (e.g., blocked exhaust slots or excessive storage), the laboratory worker should make the recommended changes and call EHS at 258-5294 to have the hood resurveyed.

If maintenance is necessary, the laboratory worker may send a copy of the written notice to the building Special Facilities staff to request maintenance. EHS does not initiate maintenance or ensure that it is completed. Special Facilities will contact EHS when the work is complete to have the hood resurveyed.

Requesting Maintenance

Providing maintenance for fume hoods is a function of the Facilities Department, and is performed by Special Facilities personnel and the MacMillan shops. Since the hood user is the person most aware of how a hood is being used on a day to day basis, it is the responsibility of the hood user to determine that maintenance is necessary and to request that it be performed.

If a hood user believes that the hood is not performing adequately, the following steps should be taken:

  1. An inadequate face velocity may result from obstructions to the airflow in the hood. These may be caused by large quantities of equipment in the hood or by paper or other material drawn into the exhaust slots. The user should first check for such obstructions and remove or modify them.
  2. The user may obtain initial maintenance through Special Facilities. If Special Facilities is unable to correct the problem, they will seek assistance from the MacMillan maintenance shops.
  3. The hood sash should be lowered until repairs are complete. Place a sign on the hood reminding users not to use the hood.
  4. If maintenance efforts are not sufficient to correct the deficiency, engineering changes may be necessary. When notified of such a situation, the user or a department representative should request an evaluation of the problem by the Facilities Engineering Department.


Other Laboratory Exhaust Systems (top)

Many laboratories use equipment and apparatus that can generate airborne contaminants, but cannot be used within a fume hood. Examples include gas chromatographs, ovens, and vacuum pumps.

Other types of local exhaust ventilation systems may be required to control contaminants generated by these operations. Such systems must not be installed without explicit approval of the building facility manager, Facilities Engineering and/or maintenance personnel. See Common Misuses of a Fume Hood for more information.

Elephant Trunks

An elephant trunk is a flexible duct or hose connected to an exhaust system. It can only capture contaminants that are very close to the inlet of the hose, typically less than a distance equal to one half of the diameter of the duct.

Elephant trunks can be effective for capturing discharges from gas chromatographs, pipe nipples or the end of tubing. However, the effectiveness of the elephant trunk should be carefully evaluated before they are used to control releases of hazardous substances.

Canopy Hoods

A canopy hood in a laboratory is constructed in a similar fashion to the overhead canopy hoods seen in kitchens. In order for the canopy hood to be able to capture contaminants, the hood requires a relatively large volume of air movement, making them somewhat costly to operate. The canopy hood works best when the thermal or buoyant forces exist to move the contaminant up to the hood capture zone.

Canopy Hood

One of the biggest problems with canopy hoods is that, in most cases, they are designed such that the contaminated air passes through the individual's breathing zone. The airflow is easily disrupted by cross currents of air.

For the most part, canopy hoods should only be used for exhaust of non-hazardous substances.

Slot Hoods

There are many types of slot hoods, each suited for different types of operations. In general, a slot hood requires less airflow than a canopy hood and is much more effective than an elephant trunk or canopy hood, when installed properly.

Slot Hood

Slot hoods are best used for operations that require more working room than a fume hood and where a limited number of low toxicity chemicals are used. The placement of the opening(s) and the velocity of airflow are based on the application, particularly dependent upon the vapor density of the chemical(s).

Examples of good uses for slot hoods are darkrooms and acid dipping operations.

Downdraft Hoods

Downdraft hoods or necropsy tables are specially designed work areas with ventilation slots on the sides of the work area. This type of system is useful for animal perfusions and other uses of chemicals with vapor densities heavier than air.

Downdraft Hood

Toxic Gas Cabinets

Highly toxic or odorous gases should be used and stored in gas cabinets.In the event of aleak or rupture, a gas cabinet will prevent the gas from contaminating the laboratory.

Gas cabinets should be connected to laboratory exhaust ventilation using hard duct, ratherthan elephant tubing, since such tubing is more likely to develop leaks. Coaxial tubing should be used for delivering gas from the cylinder to the apparatus. Coaxial tubing consists of an internal tube containing the toxic gas, inside another tube. In between the two sets of tubing is nitrogen, which is maintained at a pressure higher than the delivery pressure of the toxic gas. This ensures that, in the event of a leak in the inner tubing, the gas will not leak into the room.

Gas Cabinet

Glove Box

There are two general types of glove boxes, one operating under negative pressure, the other operating under positive pressure. Glove boxes consist of a small chamber with sealed openings fitted with arm-length gloves. The materials are placed inside the chamber and manipulated using the gloves.

Laboratory Glovebox

A glove box operating under negative pressure is used for highly toxic gases, when a fume hood might not offer adequate protection. A rule of thumb is that a fume hood will offer protection for up to 10,000 times the immediately hazardous concentration of a chemical. The airflow through the box is relatively low, and the exhaust usually must be filtered or scrubbed before release into the exhaust system.

A glove box operating under positive pressure may be used for experiments that require protection from moisture or oxygen. If this type of glove box is to be used with hazardous chemicals, the glove box must be tested for leaks before each use. A pressure gauge should be installed to be able to check the integrity of the system.

Biosafety Cabinets

A conventional fume hood should not be used for work with viable biological agents. A biosafety cabinet is specially designed and constructed to offer protection to both the worker and the biological materials.

biosafety cabinetsBiosafety cabinet flow

Similarly, a biosafety cabinet should generally not be used for work with hazardous chemicals. Most biosafety cabinets exhaust the contaminated air through high efficiency particulate air (HEPA) filters back into the laboratory. This type of filter will not contain most hazardous materials, particularly gases, fumes or vapors. Even when connected to the building exhaust system, a ducted biosafety cabinet may not achieve a face velocity of 95 - 125 feet per minute, making it inappropriate for use with hazardous chemicals.

Ductless Fume Hoods

Use of a "ductless fume hood" is strongly discouraged. These devices work by using a fan to draw air into a chamber, through one or more filters, and back into the laboratory. EHS and several professional safety and engineering organizations do not recommend the use of ductless fume hoods for several reasons. First, it is difficult to determine whether the filters are functioning adequately or need to be changed; thus, the potential for recirculating toxic materials into the laboratory is significant. In the event of a chemical spill, the hood is usually not able to contain the spilled material or the potentially high concentrations of chemical vapors.

Second, the face velocity of the hood is normally below 80 feet per minute. The hood is normally designed such that the air does not flow smoothly and evenly through the hood. Both of these characteristics make it likely for disruption of airflow or turbulence, causing unfiltered air to leak into the laboratory.

Clean Benches

Clean benches are similar to appearance as a fume hood however do not exhaust air from the laboratory. A clean bench is a device that draws air from the lab through a HEPA filter and vents the filtered air downwards onto a work surface to keep the materials within free from particulate contamination. These devices are not to be used with hazardous materials as they provide no personal protection. Do not store materials on top of this hood as this will block the filter, overload the motor, and provide poor product protection.

Clean Bench


Section 6C: Protective Equipment

SECTION 6C: Controlling Chemical Exposure


Personal Protective Equipment (top)

Personal protective equipment (PPE) is special gear used to protect the wearer from specific hazards of a hazardous substance. It is a last resort protection system, to be used when substitution or engineering controls are not feasible. PPE does not reduce or eliminate the hazard, protects only the wearer, and does not protect anyone else.

Personal Protective Equipment
PPE includes gloves, respiratory protection, eye protection, and protective clothing. The need for PPE is dependent upon the type of operations and the nature and quantity of the materials in use, and must be assessed on a case by case basis. Workers who rely on PPE must understand the functioning, proper use, and limitations of the PPE used.


Eye Protection (top)

Safety Glasses

Safety glasses look very much like normal glasses buy have lenses that are impact resistant and frames that are far stronger than standard streetwear glasses. Safety glasses with proper impact and shatter resistance will be marked "Z87" on the frame or lens. Safety glasses must have side shields and should be worn whenever there is the possibility of objects striking the eye, such as particles, glass, or metal shards. Many potential eye injuries have been avoided by wearing safety glasses. See Anecdotes for accounts of a few of these incidents.

Standard streetwear eyeglasses fitted with side shields are not sufficient. Workers who are interested in obtaining prescription safety glasses should contact EHS at 8-5294. Safety glasses come in a variety of styles to provide the best fit and comfort, including some designed to fit over prescription glasses.

Safety glasses do not provide adequate protection from significant chemical splashes. They do not seal to the face, resulting in gaps at the top, bottom and sides, where chemicals may seep through (see Anecdotes for an actual incident where this occurred). Safety glasses may be adequate when the potential splash is minimal, such as when opening eppendorf tubes.

Safety glasses are also not appropriate for dusts and powders, which can get by the glasses in ways similar to those described above. Safety goggles are best used for this type of potential exposure.

Chemical Splash Goggles

Chemical Splash Goggles should be worn when there is potential for splash from a hazardous material. Like safety glasses, goggles are impact resistant. Chemical splash goggles should have indirect ventilation so hazardous substances cannot drain into the eye area. Some may be worn over prescription glasses.

Goggles come in a variety of styles for maximum comfort and splash protection. Visorgogs are a hybrid of a goggle and safety glasses. They offer more splash protection than safety glasses, but not as much as goggles. They fit close to the face, but do not seal at the bottom as goggles do.

Face Shields

Face shields are in order when working with large volumes of hazardous materials, either for protection from splash to the face or flying particles. Face shields must be used in conjunction with safety glasses or goggles. A few incidents where a face shield would have prevented injury are described in Anecdotes.

Contact Lenses

Contact lenses may be worn in the laboratory, but do not offer any protection from chemical contact. If a contact lens becomes contaminated with a hazardous chemical, rinse the eye(s) using an eyewash and remove the lens immediately. Contact lenses that have been contaminated with a chemical must be discarded.

This particularly recommendation runs counter to what most of us were taught previously.  However, studies have shown that contact lenses are safe to wear in the laboratory environment.  For more information, see the American Optometric Association guidelines.

Protective Clothing & Footwear (top)

Protective Clothing

When the possibility of chemical contamination exists, protective clothing that resists physical and chemical hazards should be worn over street clothes. Lab coats are appropriate for minor chemical splashes and solids contamination, while plastic or rubber aprons are best for protection from corrosive or irritating liquids. Disposable outer garments (i.e., Tyvek suits) may be useful when cleaning and decontamination of reusable clothing is difficult.

Loose clothing (such as overlarge lab coats or ties), skimpy clothing (such as shorts), torn clothing and unrestrained hair may pose a hazard in the laboratory.


Closed-toed shoes should be worn at all times in buildings where chemicals are stored or used. Perforated shoes, sandals or cloth sneakers should not be worn in laboratories or where mechanical work is conducted. Such shoes offer no barrier between the laboratory worker and chemicals or broken glass.

Chemical resistant overshoes or boots may be used to avoid possible exposure to corrosive chemical or large quantities of solvents or water that might penetrate normal footwear (e.g., during spill cleanup). Leather shoes tend to absorb chemicals and may have to be discarded if contaminated with a hazardous material.

Although generally not required in most laboratories, steel-toed safety shoes may be necessary when there is a risk of heavy objects falling or rolling onto the feet, such as in bottle-washing operations or animal care facilities.


Gloves (top)

Assorted Gloves

Choosing the appropriate hand protection can be a challenge in a laboratory setting. Considering the fact that dermatitis or inflammation of the skin accounts for 40-45% of all work-related diseases, selecting the right glove for the job is important.

Not only can many chemicals cause skin irritation or burns, but also absorption through the skin can be a significant route of exposure to certain chemicals. Dimethyl sulfoxide (DMSO), nitrobenzene, and many solvents are examples of chemicals that can be readily absorbed through the skin into the bloodstream, where the chemical may cause harmful effects.

When Should Gloves Be Worn

Protective gloves should be worn when handling hazardous materials, chemicals of unknown toxicity, corrosive materials, rough or sharp-edged objects, and very hot or very cold materials. When handling chemicals in a laboratory, disposable latex, vinyl or nitrile examination gloves are usually appropriate for most circumstances. These gloves will offer protection from incidental splashes or contact.

When working with chemicals with high acute toxicity, working with corrosives in high concentrations, handling chemicals for extended periods of time or immersing all or part of a hand into a chemical, the appropriate glove material should be selected, based on chemical compatibility.

Selecting the Appropriate Glove Material

When selecting the appropriate glove, the following characteristics should be considered:

  • degradation rating
  • breakthrough time
  • permeation rate

Degradation is the change in one or more of the physical properties of a glove caused by contact with a chemical. Degradation typically appears as hardening, stiffening, swelling, shrinking or cracking of the glove. Degradation ratings indicate how well a glove will hold up when exposed to a chemical. When looking at a chemical compatibility chart, degradation is usually reported as E (excellent), G (good), F (fair), P (poor), NR (not recommended) or NT (not tested).

Breakthrough time is the elapsed time between the initial contact of the test chemical on the surface of the glove and the analytical detection of the chemical on the inside of the glove.

Permeation rate is the rate at which the test chemical passes through the glove material once breakthrough has occurred and equilibrium is reached. Permeation involves absorption of the chemical on the surface of the glove, diffusion through the glove, and desorption of the chemical on the inside of the glove. Resistance to permeation rate is usually reported as E (excellent), G (good), F (fair), P (poor) or NR (not recommended). If chemical breakthrough does not occur, then permeation rate is not measured and is reported ND (none detected).

Manufacturers stress that permeation and degradation tests are done under laboratory test conditions, which can vary significantly from actual conditions in the work environment. Users may opt to conduct their own tests, particularly when working with highly toxic materials.

For mixtures, it is recommended that the glove material be selected based on the shortest breakthrough time.

The following table includes major glove types and their general uses. This list is not exhaustive.

Glove Material General Uses
Butyl Offers the highest resistance to permeation by most gases and water vapor. Especially suitable for use with esters and ketones.
Neoprene Provides moderate abrasion resistance but good tensile strength and heat resistance. Compatible with many acids, caustics and oils.
Nitrile Excellent general duty glove. Provides protection from a wide variety of solvents, oils, petroleum products and some corrosives. Excellent resistance to cuts, snags, punctures and abrasions.
PVC Provides excellent abrasion resistance and protection from most fats, acids, and petroleum hydrocarbons.
PVA Highly impermeable to gases. Excellent protection from aromatic and chlorinated solvents. Cannot be used in water or water-based solutions.
Viton Exceptional resistance to chlorinated and aromatic solvents. Good resistance to cuts and abrasions.
Silver Shield Resists a wide variety of toxic and hazardous chemicals. Provides the highest level of overall chemical resistance.
Natural rubber Provides flexibility and resistance to a wide variety of acids, caustics, salts, detergents and alcohols.

Where to Find Compatibility Information

Most glove manufacturers have chemical compatibility charts available for their gloves. These charts may be found in laboratory safety supply catalogs such as Fisher Scientific and Lab Safety Supply. Best Gloves offers copies of their glove compatibility charts upon request. To obtain a copy, call them directly at 800-241-0323. Best Gloves also has a great deal of information available on their web site, including a downloadable glove selection program.

Most safety data sheets (SDS) recommend the most protective glove material in their Protective Equipment section. There are MSDSs for many laboratory chemicals available on the web through the EHS home page.

EHS also has a computer program with glove compatibility information for hundreds of chemicals. Contact EHS at 258-5294 for more information.

Other Considerations

There are several factors besides glove material to consider when selecting the appropriate glove. The amount of dexterity needed to perform a particular manipulation must be weighed against the glove material recommended for maximum chemical resistance. In some cases, particularly when working with delicate objects where fine dexterity is crucial, a bulky glove may actually be more of a hazard.

Where fine dexterity is needed, consider double gloving with a less compatible material, immediately removing and replacing the outer glove if there are any signs of contamination. In some cases, such as when wearing Silver Shield gloves, it may be possible to wear a tight-fitting glove over the loose glove to increase dexterity.

Glove thickness, usually measured in mils or gauge, is another consideration. A 10-gauge glove is equivalent to 10 mils or 0.01 inches. Thinner, lighter gloves offer better touch sensitivity and flexibility, but may provide shorter breakthrough times. Generally, doubling the thickness of the glove quadruples the breakthrough time.

Glove length should be chosen based on the depth to which the arm will be immersed or where chemical splash is likely. Gloves longer than 14 inches provide extra protection against splash or immersion.

Glove size may also be important. One size does not fit all. Gloves which are too tight tend to cause fatigue, while gloves which are too loose will have loose finger ends which make work more difficult. The circumference of the hand, measured in inches, is roughly equivalent to the reported glove size. Glove color, cuff design, and lining should also be considered for some tasks.

Glove Inspection, Use and Care

All gloves should be inspected for signs of degradation or puncture before use. Test for pinholes by blowing or trapping air inside and rolling them out. Do not fill them with water, as this makes the gloves uncomfortable and may make it more difficult to detect a leak when wearing the glove.

Disposable gloves should be changed when there is any sign of contamination. Reusable gloves should be washed frequently if used for an extended period of time.

While wearing gloves, be careful not to handle anything but the materials involved in the procedure. Touching equipment, phones, wastebaskets or other surfaces may cause contamination. Be aware of touching the face, hair, and clothing as well.

Before removing them, wash the outside of the glove. To avoid accidental skin exposure, remove the first glove by grasping the cuff and peeling the glove off the hand so that the glove is inside out. Repeat this process with the second hand, touching the inside of the glove cuff, rather than the outside. Wash hands immediately with soap and water.

Follow the manufacturer’s instructions for washing and caring for reusable gloves.

Proper Glove Removal

Gloves should be removed avoiding skin contact with the exterior of the glove and possible contamination. Disposable gloves should be removed as follows:

  • Grasp the exterior of one glove with your other gloved hand.
  • Carefully pull the glove off your hand, turning it inside-out. ............ The contamination is now on the inside.
  • Ball the glove up and hold in your other gloved hand.
  • Slide your ungloved finger into the opening of the other glove. ........ Avoid touching the exterior.
  • Carefully pull the glove off your hand, turning it inside out again. .... All contamination is contained.
  • Discard appropriately.

Glove Removal

Latex Gloves and Related Allergies

Allergic reactions to natural rubber latex have been increasing since 1987, when the Centers for Disease Control recommended the use of universal precautions to protect against potentially infectious materials, bloodborne pathogens and HIV. Increased glove demand also resulted in higher levels of allergens due to changes in the manufacturing process. In addition to skin contact with the latex allergens, inhalation is another potential route of exposure. Latex proteins may be released into the air along with the powders used to lubricate the interior of the glove.

In June, 1997, the National Institute of Occupational Safety and Health (NIOSH) issued an alert Preventing Allergic Reactions to Latex in the Workplace (publication number DHHS (NIOSH) 97-135).

Latex exposure symptoms include skin rash and inflammation, respiratory irritation, asthma and shock. The amount of exposure needed to sensitize an individual to natural rubber latex is not known, but when exposures are reduced, sensitization decreases.

NIOSH recommends the following actions to reduce exposure to latex:

  • Whenever possible, substitute another glove material.
  • If latex gloves must be used, choose reduced-protein, powder-free latex gloves.
  • Wash hands with mild soap and water after removing latex gloves.

    Hearing Protection (top)

    Most laboratory equipment and operations do not produce noise levels that require the use of hearing protection, with the exception of some wind tunnels, as described below. Princeton University has a Hearing Conservation Program in place for individuals who are exposed to noise levels equal to or exceeding the OSHA action level of 85 decibels (dBA) averaged over eight hours, per the OSHA Occupational Noise Standard. This program includes workplace monitoring, personal exposure monitoring, annual audiometric testing, use of hearing protection and annual training.

    Laboratory workers who would like to use hearing protection for noise levels below the action level may do so without enrollment in the Hearing Conservation Program. Using hearing protection, such as earplugs, earmuffs or hearing bands, can improve communication or provide comfort to the worker in a noisy environment.

    The most common noisy equipment in the laboratories are ultrasonicators and wind tunnels. EHS has measured noise levels of several ultrasonicators used in the laboratories and found that noise levels were well below 85 dBA, averaged over eight hours. Some of the wind tunnels, particularly the supersonic wind tunnels, are capable of very high noise levels. Users should check with the principal investigator or EHS to determine whether they need to be enrolled in the Hearing Conservation Program.

    For more information about the Hearing Conservation Program, see Section B5, Noise and Hearing Conservation, of the Princeton University Health and Safety Guide. Contact EHS at 258-5294 to request noise monitoring.

    Respiratory Protection (top)

    A respirator may only be used when engineering controls, such as general ventilation or a fume hood, are not feasible or do not reduce the exposure of a chemical to acceptable levels. Since the use of a respirator is regulated by the OSHA Respiratory Protection Standard, respirator use at Princeton is subject to prior review by EHS, according to university policy.

    Any worker who believes that respiratory protection is needed must notify EHS for evaluation of the hazard and enrollment in the Respiratory Protection Program. This program involves procedures for respirator selection, medical assessment of employee health, employee training, proper fitting, respirator inspection and maintenance, and recordkeeping.

    Use of a paper or cloth dust mask (left-most in above picture) is allowed without enrolling in the Respiratory Protection Program. However, if you believe you need to upgrade to a tight-fitting respirator, you must contact EHS prior. Tight fitting respirators are typically made of silicone or rubber and have filter cartridges or supplied air for breathing.

    Self-contained breathing apparatus (SCBA) is available in E-Quad for use by only trained individuals for changing out cylinders of highly toxic gases and cleaning up chemical spills. They are not to be used for response to a fire. Training is offered every Spring and Fall in E-Quad. Contact EHS (8-5294) if you are interested and are not on the mailing list for this training.

    For more information, see Section C4, Respiratory Protection, in the Princeton University Health and Safety Guide.

    Section 7: Safe Work Practices and Procedures



    7A: General Work Practices


    Before You Begin (top)

    Every laboratory worker should observe the following rules:

    1. Know the potential hazards and appropriate safety precautions before beginning work. Ask and be able to answer the following questions:
      • What are the hazards?
      • What are the worst things that could happen?
      • What do I need to do to be prepared?
      • What work practices, facilities or personal protective equipment are needed to minimize the risk?
    2. Know the location and how to use emergency equipment, including safety showers and eyewash stations.
    3. Never block safety equipment or doors and keep aisles clear and free from tripping hazards.
    4. Familiarize yourself with the emergency response procedures, facility alarms and building evacuation routes.
    5. Know the types of personal protective equipment available and how to use them for each procedure.
    6. Be alert to unsafe conditions and actions and bring them to the attention of your supervisor or lab manager immediately so that corrections can be made as soon as possible.
    7. Prevent pollution by following waste disposal procedures. Chemical reactions may require traps or scrubbing devices to prevent the release of toxic substances to the laboratory or to the environment.
    8. Position and clamp reaction apparatus thoughtfully in order to permit manipulation without the need to move the apparatus until the entire reaction is completed. Combine reagents in the appropriate order and avoid adding solids to hot liquids.


    Chemical Storage (top)

    Many local, state and federal regulations have specific requirements that affect the handling and storage of chemicals in laboratories.

    General Considerations

    In general, store materials and equipment in cabinets and on shelving provided for such storage.

    • Avoid storing materials and equipment on top of cabinets. If you must place things there, however, you must maintain a clearance of at least 18 inches from the sprinkler heads or (if no sprinkler heads are present) 24 inches from the ceiling.
    • Be sure that the weight of the chemicals does not exceed the load capacity of the shelf or cabinet. Some incidents where shelving or a cabinet collapsed due to overload are described in Anecdotes.
    • Wall-mounted shelving must have heavy-duty brackets and standards. This type of shelving is not recommended for chemical storage.
    • Cabinets for chemical storage must be of solid, sturdy construction, preferably hardwood or metal.
    • Do not store materials on top of high cabinets where they will be hard to see or reach.
    • Do not store corrosive liquids above eye level.
    • Provide a specific storage location for each type of chemical, and return the chemicals to those locations after each use.
    • Avoid storing chemicals in the workspace within a laboratory hood, except for those chemicals currently in use.
    • If a chemical does not require a ventilated cabinet, store it inside a closable cabinet or on a shelf that has a lip to prevent containers from sliding off in the event of an accident or fire.
    • Do not expose chemicals to heat or direct sunlight.
    • Observe all precautions regarding the storage of incompatible chemicals.
    • Use corrosion resistant storage trays or secondary containers to collect materials if the primary container breaks or leaks.
    • Distinguish between refrigerators used for chemical storage and refrigerators used for food storage. Each refrigerator should be labeled "No Food" or "Food Only". Labels are available from EHS by calling 8-5294.
    • Do not store flammable liquids in a refrigerator unless it is approved for such storage. Such refrigerators are designed with non-sparking components to avoid an explosion.
    • Chemical storage cabinets located outside the laboratory (e.g., in hallways) should be labeled with the name of the laboratory group that owns and uses it.

    Segregation of Chemicals

    Incompatible chemicals should not be stored together. Storing chemicals alphabetically, without regard to compatibility, can increase the risk of a hazardous reaction, especially in the event of container breakage. In addition to the Chemical Compatibility Chart below, there are several resources available, both in print and on-line, including the National Oceanic and Atmospheric Administration Chemical Reactivity Worksheet.

    Use common sense when setting up chemical storage. Segregation that disrupts normal workflow can increase the potential for spills.

    There are several possible storage plans for segregation. In general, dry reagents, liquids and compressed gases should be stored separately, then by hazard class, then alphabetically (if desired).

    Segregate dry reagents as follows:

    • Oxidizing salts
    • Flammable solids
    • Water-reactive solids
    • All other solids

    Segregate liquids as follows:

    Segregate compressed gases as follows:

    • Toxic gases
    • Flammable gases
    • Oxidizing and inert gases

    Chemical Incompatibility Chart

    Mixing these chemicals purposely or as a result of a spill can result in heat, fire, explosion, and/or toxic gases.  This is a partial list.


    Acetic Acid Chromic Acid, nitric acid, hydroxyl-containing compounds, ethylene glycol, perchloric acid, peroxides, and permanganates. 
    Acetone Bromine, chlorine, nitric acid, sulfuric acid, and hydrogen peroxide.
    Acetylene Bromine, chlorine, copper, mercury, fluorine, iodine, and silver.
    Alkaline and Alkaline Earth Metals such as calcium, lithium, magnesium, sodium, potassium, powdered aluminum Carbon dioxide, carbon tetrachloride and other chlorinated hydrocarbons, water, Bromine, chlorine, fluorine, and iodine.  Do not use CO2, water or dry chemical extinguishers.  Use Class D extinguisher (e.g., Met-L-X) or dry sand.
    Aluminum and its Alloys (especially powders) Acid or alkaline solutions, ammonium persulfate and water, chlorates, chlorinated compounds, nitrates, and organic compounds in nitrate/nitrate salt baths. 
    Ammonia (anhydrous) Bromine, chlorine, calcium hypochlorite, hydrofluoric acid, iodine, mercury, and silver.
    Ammonium Nitrate Acids, metal powders, flammable liquids, chlorates, nitrates, sulfur and finely divided organics or other combustibles. 
    Aniline Hydrogen peroxide or nitric acid.
    Bromine  Acetone, acetylene, ammonia, benzene, butadiene, butane and other petroleum gases, hydrogen, finely divided metals, sodium carbide, turpentine. 
    Calcium Oxide Water
    Carbon (activated)  Calcium hypochlorite, all oxidizing agents.
    Caustic (soda) Acids (organic and inorganic).
    Chlorates or Perchlorates Acids, aluminum, ammonium salts, cyanides, phosphorous, metal powders, oxidizable organics or other combustibles, sugar, sulfides, and sulfur.
    Chlorine  Acetone, acetylene, ammonia, benzene, butadiene, butane and other petroleum gases, hydrogen, finely divided metals, sodium carbide, turpentine.
    Chlorine Dioxide Ammonia, methane, phosphine, hydrogen sulfide. 
    Chromic Acid Acetic acid, naphthalene, camphor, alcohol, glycerine, turpentine and other flammable liquids.
    Copper Acetylene, hydrogen peroxide. 
    Cumene Hydroperoxide Acids 
    Cyanides Acids
    Flammable Liquids Ammonium nitrate, chromic acid, hydrogen peroxide, nitric acid, sodium peroxide, bromine, chlorine, fluorine, iodine.
    Fluorine  Isolate from everything.
    Hydrazine Hydrogen peroxide, nitric acid, and other oxiding agents.
    Hydrocarbons Bromine, chlorine, chromic acid, fluorine, hydrogen peroxide, and sodium peroxide.
    Hydrocyanic Acid Nitric acid, alkali.
    Hydrofluoric Acid Ammonia, aqueous or anhydrous.
    Hydrogen Peroxide (anhydrous) Chromium, copper, iron, most metals or their salts, aniline, any flammable liquids, combustible materials, nitromethane, and all other organic material.
    Hydrogen Sulfide  Fuming nitric acid, oxidizing gases.
    Iodine Acetylene, ammonia (aqueous or anhydrous), hydrogen.
    Mercury  Acetylene, alkali metals, ammonia, fulminic acid, nitric acid with ethanol, hydrogen, oxalic acid. 
    Nitrates  Combustible materials, esters, phosphorous, sodium acetate, stannous chloride, water, zinc powder. 
    Nitric acid (concentrated) Acetic acid, acetone, alcohol, aniline, chromic acid, flammable gases and liquids, hydrocyanic acid, hydrogen sulfide and nitratable substances. 
    Nitrites Potassium or sodium cyanide.
    Nitroparaffins  Inorganic bases, amines. 
    Oxalic acid  Silver, mercury, and their salts.
    Oxygen (liquid or enriched air) Flammable gases, liquids, or solids such as acetone, acetylene, grease, hydrogen, oils, phosphorous. 
    Perchloric Acid  Acetic anhydride, alcohols, bismuth and its alloys, paper, wood, grease, oils or any organic materials and reducing agents. 
    Peroxides (organic) Acid (inorganic or organic). Also avoid friction and store cold.
    Phosphorus (white) Air, oxygen.
    Phosphorus pentoxide Alcohols, strong bases, water.
    Potassium Air (moisture and/or oxygen) or water, carbon tetrachloride, carbon dioxide.
    Potassium Chlorate Sulfuric and other acids. 
    Potassium Perchlorate Acids.
    Potassium Permanganate Benzaldehyde, ethylene glycol, glycerol, sulfuric acid. 
    Silver and silver salts Acetylene, oxalic acid, tartaric acid, fulminic acid, ammonium compounds. 
    Sodium See Alkali Metals
    Sodium Chlorate Acids, ammonium salts, oxidizable materials and sulfur. 
    Sodium Nitrite  Ammonia compounds, ammonium nitrate, or other ammonium salts. 
    Sodium Peroxide  Any oxidizable substances, such as ethanol, methanol, glacial acetic acid, acetic anhydride, benzaldehyde, carbon disulfide, glycerol, ethylene glycol, ethyl acetate, methyl acetate, furfural, etc. 
    Sulfides Acids.
    Sulfur  Any oxidizing materials. 
    Sulfuric Acid  Chlorates, perchlorates, permanganates, compounds with light metals such as sodium, lithium, and potassium. 
    Water  Acetyl chloride, alkaline and alkaline earth metals, their hydrides and oxides, barium peroxide, carbides, chromic acid, phosphorous oxychloride, phosphorous pentachloride, phosphorous pentoxide, sulfuric acid, sulfur trioxide. 

    Flammable Liquids

    Flammable liquids require special storage considerations. See Flammable Materials for more information.


    Mineral acids, including phosphoric, hydrochloric, nitric, sulfuric, and perchloric acid can be stored in a cabinet designed for Corrosive Acids.  These non-metallic cabinets have no internal metallic parts, acid resistant coating and a cabinet floor constructed to be able to contain spillage. Volatile acids, such as oleum or fuming nitric acid, should be stored either in an acid cabinet or in a vented cabinet, such as the fume hood base, particularly after they have been opened.  Concentrated mineral acids can be very reactive, even with each other. Concentrated acids can even react vigorously with dilute solutions of the same acid, if mixed together rapidly. For example: concentrated sulfuric acid mixed quickly with 1 molar sulfuric acid will generate a lot of heat. Different concentrated acids should be stored apart. If stored within the same cabinet, plastic trays, tubs or buckets work well to keep different acids apart within the cabinet.

    Acetic acid is an organic acid and should be stored separately from mineral acids.  Since it is also flammable, it is best stored with other flammable liquids.

    Picric Acid can form explosive salts with many metals, or by itself when dry. Perchloric Acid is an extremely powerful oxidizer and must be kept away from all organic materials, including wood. See Section 7D, Corrosives, for more information. 

    Unstable Chemicals

    Ethers and some ketones and olefins may form peroxides when exposed to air or light. Since they may have been packaged in an air atmosphere, peroxides can form even if the container has not been opened.

    Some chemicals, such as dinitroglycerine and germane, are shock-sensitive, meaning that they can rapidly decompose or explode when struck, vibrated or otherwise agitated. These compounds become more shock-sensitive with age.

    For any potentially unstable chemical:

    • On the label, write the date the container was received and the date it was opened.
    • Discard containers within 6 months of opening them.
    • Discard unopened containers after one year, unless an inhibitor was added.

    More information about unstable chemicals is available in Section 7C: Peroxide Forming Compounds and Reactives.

    Designated Areas

    Any area where particularly hazardous substances, including carcinogens, acutely toxic chemicals and reproductive toxins, are stored or used must be posted as a Designated Area. These materials should be stored separately from other chemicals, as space permits. See Section 7J: Particularly Hazardous Substances for more information.

    Compressed Gases

    Compressed gases pose a chemical hazard due to the gases themselves and a high energy source hazard due to the great amount of pressure in the cylinder. Large cylinders may weight 130 pounds or more and can pose a crush hazard to hands and feet.

    • All cylinders must be secured to a wall, bench or other support structure using a chain or strap. Alternatively, a cylinder stand may be used.
    • Segregate cylinders by gas type (e.g., flammable, inert, etc.).
    • Store cylinders away from heat sources and extreme weather conditions.

    See Section 7E: Compressed Gas Cylinders for more information.

    Combustible Materials

    Common combustible materials, such as paper, wood, corrugated cardboard cartons and plastic labware, if allowed to accumulate, can create a significant fire hazard in the laboratory. Combustible materials not stored in metal cabinets should be kept to a minimum. Store large quantities of such supplies in a separate room, if possible.


    Personal Behavior (top)

    Professional standards of personal behavior are required in any laboratory:

    • Avoid distracting or startling other workers
    • Do not allow practical jokes or horseplay
    • Use laboratory equipment only for its designated purpose
    • Do not allow visitors, including children and pets, in laboratories where hazardous substances are stored or are in use or hazardous activities are in progress.
    • Do not prepare, store (even temporarily), or consume food or beverages in any chemical laboratory
    • Do not smoke in any chemical laboratory. Additionally, be aware that tobacco products in opened packages can absorb chemical vapors.
    • Do not apply cosmetics when in the laboratory
    • Never wear or bring lab coats or jackets into areas where food is consumed.
    • Confine long hair and loose clothing in the laboratory. Wear shoes at all times. Open-toed shoes or sandals are not appropriate.
    • Under no circumstances should mouth suction be used to pipette chemicals or to start a siphon. Use a pipette bulb or a mechanical pipetting device to provide a vacuum.
    • Wash well before leaving the laboratory. Do not use solvents for washing skin.
    • Keep work areas clean and free from obstruction. Clean up spills immediately.
    • Do not block access to exits, emergency equipment, controls, electrical panels etc.
    • Avoid working alone.


    Transporting Chemicals (top)

    Spills and chemical exposure can occur if chemicals are transported incorrectly, even when moving chemicals from one part of the laboratory to another. One example of such an incident is described in Anecdotes. To avoid this type of incident, consider the following:

    • Use a bottle carrier, cart or other secondary container when transporting chemicals in breakable containers (especially 250 ml or more) through hallways or between buildings. Secondary containers are made of rubber, metal or plastic, with carrying handle(s), and are large enough to hold the entire contents of the chemical containers in the event of breakage. A variety of such containers are available from the Chemistry stockroom or from laboratory supply catalogs.
    • Transport of hazardous chemicals in individual containers exceeding four liters between buildings is strongly discouraged.
    • Transportation of hazardous chemicals in personal vehicles is strictly forbidden.
    • When moving in the laboratory, anticipate sudden backing up or changes in direction by others. If you should stumble or fall while carrying glassware or chemicals, try to project them away from yourself and others.
    • The individual transporting the chemical should be knowledgeable about the hazards of the chemical and should know how to handle a spill of the material.
    • When transporting compressed gas cylinders, the cylinder should always be strapped in a cylinder cart and the valve protected with a cover cap. Do not attempt to carry or roll cylinders from one area to another.
    • Transport chemicals in freight elevators rather than passenger elevators, if available.
    • Keep chemicals in their original packing when transporting, if possible.


    Working with Scaled-Up Reactions (top)

    Scale-up of reactions from those producing a few milligrams or grams to those producing more than 100g of a product may represent several orders of magnitude of added risk. The attitudes, procedures and controls applicable to large-scale laboratory reactions are fundamentally the same as those for smaller-scale procedures. However, differences in heat transfer, stirring effects, times for dissolution, and effects of concentration and the fact that substantial amounts of materials are being used introduce the need for special vigilance for scaled-up work. Careful planning and consultation with experienced workers to prepare for any eventuality are essential for large-scale laboratory work. See Anecdotes.

    Although it is not always possible to predict whether a scaled-up reaction has increased risk, hazards should be evaluated if the following conditions exist:

    • The starting material and/or intermediates contain functional groups that have a history of being explosive (e.g., N—N, N—O, N—halogen, O—O, and O—halogen bonds) or that could explode to give a large increase in pressure.
    • A reactant or product is unstable near the reaction or work-up temperature. A preliminary test consists of heating a small sample in a melting point tube.
    • A reaction is delayed; that is, an induction period is required.
    • Gaseous by-products are formed.
    • A reaction is exothermic. Consider what can be done to provide cooling if the reaction begins to run away.
    • A reaction requires a long reflux period. Consider what could happen if solvent is lost owing to poor condenser cooling.
    • A reaction requires temperatures below 0oC. Consider what could happen if the reaction warms to room temperature.

    In addition, thermal phenomena that produce significant effects on a larger scale may not have been detected in smaller-scale reactions and therefore could be less obvious than toxic and/or environmental hazards. Thermal analytical techniques should be used to determine whether any process modifications are necessary.


    Unattended Experiments (top)

    Laboratory operations involving hazardous substances are sometimes carried out continuously or overnight with no one present. It is the responsibility of the worker to design these experiments so as to prevent the release of hazardous substances in the event of interruptions in utility services such as electricity, cooling water, and inert gas.

    • Laboratory lights should be left on, and signs should be posted identifying the nature of the experiment and the hazardous substances in use.
    • If appropriate, arrangements should be made for other workers to periodically inspect the operation.
    • The Emergency Information Poster should include contact information for the responsible individual in the event of an emergency.
    • Carefully examine how chemicals and apparatus are stored, considering the possibility for fire, explosion or unintended reactions. A description of a fire that occurred in a fume hood when an experiment was left unattended for several days may be found in Anecdotes.


    Working Alone (top)

    Individuals using hazardous chemicals should not work alone. Another individual capable of coming to the aid of the worker should be in visual or audio contact.

    • If working alone is absolutely necessary, the worker should have a phone immediately available and should be in contact with another person (who knows that he or she is being relied upon) at least every 30 minutes.
    • If no one from the laboratory is available, the worker should coordinate with another person in the building to check in on them periodically.
    • If the research or operation is particularly hazardous such that a researcher could be severely injured or overcome by the process, a capable person must be present at all times and know to contact Public Safety at 911 or 258-3333 in event of an emergency.

    The laboratory supervisor or PI is responsible for determining whether the work requires special precautions, such as having two people in the same room for particular operations.

    Section 7B: Flammable Materials

    SECTION 7: Safe Work Practices and Procedures

    7B: Flammable Materials


    Properties of Flammable and Combustible Liquids (top)

    Flammable and combustible liquids vaporize and form flammable mixtures with air when in open containers, when leaks occur, or when heated. To control these potential hazards, several properties of these materials, such as volatility, flashpoint, flammable range and autoignition temperatures must be understood. An explanation of these terms and other properties of flammable liquids is available here. Information on the properties of a specific liquid can be found in that liquid’s material safety data sheet (SDS), or other reference material.


    Storage of Flammable and Combustible Liquids (top)

    Flammable and combustible liquids should be stored only in approved containers. Approval for containers is based on specifications developed by organizations such as the US Department of Transportation (DOT), OSHA, the National Fire Protection Agency (NFPA) or American National Standards Institute (ANSI). Containers used by the manufacturers of flammable and combustible liquids generally meet these specifications.

    Safety Cans and Closed Containers

    Many types of containers are required depending on the quantities and classes of flammable or combustible liquids in use. A safety can is an approved container of not more than 5 gallons capacity that has a spring closing lid and spout cover. Safety cans are designed to safely relieve internal pressure when exposed to fire conditions. A closed container is one sealed by a lid or other device so that liquid and vapor cannot escape at ordinary temperatures.

    Flammable Liquid Storage Cabinets

    A flammable liquid storage cabinet is an approved cabinet that has been designed and constructed to protect the contents from external fires. Storage cabinets are usually equipped with vents, which are plugged by the cabinet manufacturer. Since venting is not required by any code or the by local municipalities and since venting may actually prevent the cabinet from protecting its contents, vents should remain plugged at all times. Storage cabinets must also be conspicuously labeled "FLAMMABLE – KEEP FIRE AWAY".


    Use only those refrigerators that have been designed and manufactured for flammable liquid storage. Standard household refrigerators must not be used for flammable storage because internal parts could spark and ignite. Refrigerators must be prominently labeled as to whether or not they are suitable for flammable liquid storage.

    Storage Considerations:

    • Quantities should be limited to the amount necessary for the work in progress.
    • No more than 10 gallons of flammable and combustible liquids, combined, should be stored outside of a flammable storage cabinet unless safety cans are used. When safety cans are used, up to 25 gallons may be stored without using a flammable storage cabinet.
    • Storage of flammable liquids must not obstruct any exit.
    • Flammable liquids should be stored separately from strong oxidizers, shielded from direct sunlight, and away from heat sources. See Anecdotes for a description of an incident involving a flammable material stored near a hot plate.


    Handling Precautions (top)

    The main objective in working safely with flammable liquids is to avoid accumulation of vapors and to control sources of ignition.

    Besides the more obvious ignition sources, such as open flames from Bunsen burners, matches and cigarette smoking, less obvious sources, such as electrical equipment, static electricity and gas-fired heating devices should be considered. Accounts of a few of the fires that have occurred in our laboratories may be found in Anecdotes.

    Some electrical equipment, including switches, stirrers, motors, and relays can produce sparks that can ignite vapors. Although some newer equipment have spark-free induction motors, the on-off switches and speed controls may be able to produce a spark when they are adjusted because they have exposed contacts. One solution is to remove any switches located on the device and insert a switch on the cord near the plug end.

    Pouring flammable liquids can generate static electricity. The development of static electricity is related to the humidity levels in the area. Cold, dry atmospheres are more likely to facilitate static electricity. Bonding or using ground straps for metallic or non-metallic containers can prevent static generation.

    • Control all ignition sources in areas where flammable liquids are used. Smoking, open flames and spark producing equipment should not be used.
    • Whenever possible use plastic or metal containers or safety cans.
    • When working with open containers, use a laboratory fume hood to control the accumulation of flammable vapor.
    • Use bottle carriers for transporting glass containers.
    • Use equipment with spark-free, intrinsically safe induction motors or air motors to avoid producing sparks. These motors must meet National Electric Safety Code (US DOC, 1993) Class 1, Division 2, Group C-D explosion resistance specifications. Many stirrers, Variacs, outlet strips, ovens, heat tape, hot plates and heat guns do not conform to these code requirements.
    • Avoid using equipment with series-wound motors, since they are likely to produce sparks.
    • Do not heat flammable liquids with an open flame. Steam baths, salt and sand baths, oil and wax baths, heating mantles and hot air or nitrogen baths are preferable.
    • Minimize the production of vapors and the associated risk of ignition by flashback. Vapors from flammable liquids are denser than air and tend to sink to the floor level where they can spread over a large area.
    • Electrically bond metal containers when transferring flammable liquids from one to another. Bonding can be direct, as a wire attached to both containers, or indirect, as through a common ground system.
    • When grounding non-metallic containers, contact must be made directly to the liquid, rather than to the container.
    • In the rare circumstance that static cannot be avoided, proceed slowly to give the charge time to disperse or conduct the procedure in an inert atmosphere.


    Flammable Aerosols (top)

    Flammable liquids in pressurized containers may rupture and aerosolize when exposed to heat, creating a highly flammable vapor cloud. As with flammable liquids, these should be stored in a flammable storage cabinet.


    Flammable and Combustible Solids (top)

    Flammable solids often encountered in the laboratory include alkali metals, magnesium metal, metallic hydrides, some organometallic compounds, and sulfur. Many flammable solids react with water and cannot be extinguished with conventional dry chemical or carbon dioxide extinguishers. See Anecdotes for descriptions of incidents involving such materials.

    • Ensure Class D extinguishers, e.g., Met-L-X, are available where flammable solids are used or stored.
    • Sand can usually be used to smother a fire involving flammable solids. Keep a container of sand near the work area.
    • If a flammable, water-reactive solid is spilled onto skin, brush off as much as possible, then flush with copious amounts of water.
    • NEVER use a carbon dioxide fire extinguisher for fires involving lithium aluminum hydride (LAH). LAH reacts explosively with carbon dioxide.


    Catalyst Ignition (top)

    Some hydrogenated catalysts, such as palladium, platinum oxide, and Raney nickel, when recovered from hydrogenation reactions, may become saturated with hydrogen and present a fire or explosion hazard.

    • Carefully filter the catalyst.
    • Do not allow the filter cake to become dry.
    • Place the funnel containing moist catalyst into a water bath immediately.

    Purge gases, such as nitrogen or argon, may be used so that the catalyst can be filtered and handled in an inert atmosphere.


    Section 7C: Peroxide Forming Compounds and Reactives

    SECTION 7: Safe Work Practices and Procedures

    7C: Peroxide Forming Compounds and Reactives

    Certain chemicals can form dangerous peroxides on exposure to air and light. Since they are sometimes packaged in an atmosphere of air, peroxides can form even though the containers have not been opened. Peroxides may detonate with extreme violence when concentrated by evaporation or distillation, when combined with other compounds, or when disturbed by unusual heat, shock or friction. Formation of peroxides in ethers is accelerated in opened and partially emptied containers. Refrigeration will not prevent peroxide formation and stabilizers will only retard formation.

    Peroxide formation may be detected by visual inspection for crystalline solids or viscous liquids, or by using chemical methods or specialized kits for quantitative or qualitative analysis. If you suspect that peroxides have formed, do not open the container to test since peroxides deposited on the threads of the cap could detonate.

    See Anecdotes for an account of an incident in our laboratories involving peroxide detonation.

    Recommended Work Practices (top)

    The following recommendations should be followed to control the hazards of peroxides.

    • Know the properties and hazards of all chemicals you are using through adequate research and study, including reading the label and SDS.
    • Inventory all chemical storage at least twice a year to detect forgotten items, leaking containers, and those that need to be discarded.
    • Identify chemicals that form peroxides or otherwise deteriorate or become more hazardous with age or exposure to air. Label containers with the date received, the date first opened and the date for disposal as recommended by the supplier.
    • Minimize peroxide formation in ethers by storing in tightly sealed containers placed in a cool place in the absence of light. Do not store ethers at or below the temperature at which the peroxide freezes or the solution precipitates.
    • Choose the size container that will ensure use of the entire contents within a short period of time.
    • Visually or chemically check for peroxides of any opened containers before use.
    • Clean up spills immediately. The safest method is to absorb the material onto vermiculite or a similar loose absorbent.
    • When working with peroxidizable compounds, wear impact-resistant safety eyewear and face shields. Visitor specs are intended only for slight and brief exposure, and should not be used when working with peroxidizable compounds.
    • Do not use solutions of peroxides in volatile solvents under conditions in which the solvent might be vaporized. This could increase the concentration of peroxide in the solution.
    • Do not use metal spatulas or magnetic stirring bars (which may leach out iron) with peroxide forming compounds, since contamination with metals can lead to explosive decomposition. Ceramic, Teflon or wooden spatulas and stirring blades are usually safe to use.
    • Do not use glass containers with screw-top lids or glass stoppers. Polyethylene bottles with screw-top lids may be used.

    Examples of Peroxidizable Compounds (top)

    Peroxide Hazard on Storage: Discard After Three Months
    Divinyl acetylene

    Divinyl ether

    Isopropyl ether

    Potassium metal

    Sodium amide 

    Vinylidene chloride

    Peroxide Hazard on Concentration: Discard After One Year







    Diethyl ether

    Diethylene glycol dimethyl ether (diglyme)


    Ethylene glycol dimethyl ether (glyme)


    Methyl acetylene


    Methyl isobutyl ketone

    Tetrahydronaphtalene (Tetralin)


    Vinyl ethers

    Hazardous Due to Peroxide Initiation of Polymerization*: Discard After One Year
    Acrylic acid





    Methyl methacrylate



    Vinyl acetylene

    Vinyl acetate

    Vinyl chloride

    Vinyl pyridine

    * Under storage conditions in the liquid state the peroxide-forming potential increases and certain of these monomers (especially butadiene, chloroprene, and tetrafluoroethylene) should be discarded after three months.

    Detection of Peroxides (top)

    If there is any suspicion that peroxide is present, do not open the container or otherwise disturb the contents. Call EHS for disposal. The container and its contents must be handled with extreme care. If solids, especially crystals, for example, are observed either in the liquid or around the cap, peroxides are most likely present.

    If no peroxide is suspected but the chemical is a peroxide former, the chemical can be tested by the lab to ensure no peroxide has formed.

    • Peroxide test strips, which change color to indicate the presence of peroxides, may be purchased through most laboratory reagent distributors.  For proper testing, reference the manufacturer’s instruction.  Do not perform a peroxide test on outdated materials that potentially have dangerous levels of peroxide formation

    Removal of Peroxides (top)

    If peroxides are suspected, the safest route is to alert EHS for treatment and disposal of the material. Attempting to remove peroxides may be very dangerous under some conditions.


    Peroxide Forming Chemicals Poster (2018)

    Testing Labels for Peroxide Forming Chemicals:


    For more information:

    Additional resources for chemicals that exhibit explosive properties, peroxide formation and container pressurization hazards.

    Section 7D: Corrosive Materials

    SECTION 7: Safe Work Practices and Procedures

    7D: Corrosive Materials

    Many chemicals commonly used in the laboratory are corrosive or irritating to body tissue. They present a hazard to the eyes and skin by direct contact, to the respiratory tract by inhalation or to the gastrointestinal system by ingestion. Anecdotes offers incidents involving chemical burns from incorrectly handling corrosives.


    Corrosive Liquids (top)

    Corrosive liquids (e.g. mineral acids, alkali solutions and some oxidizers) represent a very significant hazard because skin or eye contact can readily occur from splashes and their effect on human tissue generally takes place very rapidly. Bromine, sodium hydroxide, sulfuric acid and hydrogen peroxide are examples of highly corrosive liquids. See Chemical Specific Protocols for specific corrosive liquids such as Hydrofluoric Acid and Phenol.

    The following should be considered:

    1. The eyes are particularly vulnerable. It is therefore essential that approved eye and face protection be worn in all laboratories where corrosive chemicals are handled.

    2. Gloves and other chemically resistant protective clothing should be worn to protect against skin contact.

    3. To avoid a flash steam explosion due to the large amount of heat evolved, always add acids or bases to water (and not the reverse).

    4. Acids and bases should be segregated for storage.

    5. Liquid corrosives should be stored below eye level.

    6. Adequate quantities of spill control materials should be readily available. Specialized spill kits for acids and bases are available through most chemical and laboratory safety supply catalogs.


    Corrosive Gases and Vapors (top)

    Corrosive gases and vapors are hazardous to all parts of the body; certain organs (e.g. the eyes and the respiratory tract) are particularly sensitive. The magnitude of the effect is related to the solubility of the material in the body fluids. Highly soluble gases (e.g. ammonia, hydrogen chloride) cause severe nose and throat irritation, while substances of lower solubility (e.g. nitrogen dioxide, phosgene, sulfur dioxide) can penetrate deep into the lungs.

    1. Warning properties such as odor or eye, nose or respiratory tract irritation may be inadequate with some substances. Therefore, they should not be relied upon as a warning of overexposure.
    2. Perform manipulations of materials that pose an inhalation hazard in a chemical fume hood to control exposure or wear appropriate respiratory protection.
    3. Protect all exposed skin surfaces from contact with corrosive or irritating gases and vapors.
    4. Regulators and valves should be closed when the cylinder is not in use and flushed with dry air or nitrogen after use.
    5. When corrosive gases are to be discharged into a liquid, a trap, check valve, or vacuum break device should be employed to prevent dangerous reverse flow.


    Corrosive Solids (top)

    Corrosive solids, such as sodium hydroxide and phenol, can cause burns to the skin and eyes. Dust from corrosive solids can be inhaled and cause irritation or burns to the respiratory tract. Many corrosive solids, such as potassium hydroxide and sodium hydroxide, can produce considerable heat when dissolved in water.

    1. Wear gloves and eye protection when handling corrosive solids.
    2. When mixing with water, always slowly add the corrosive solid to water, stirring continuously. Cooling may be necessary.
    3. If there is a possibility of generating a significant amount of dust, conduct work in a fume hood.

    Section 7E: Compressed Gases

    SECTION 7: Safe Work Practices and Procedures

    7E: Compressed Gases


    Compressed gases can be toxic, flammable, oxidizing, corrosive, inert or a combination of hazards. In addition to the chemical hazards, compressed gases may be under a great deal of pressure. The amount of energy in a compressed gas cylinder makes it a potential rocket. Appropriate care in the handling and storage of compressed gas cylinders is essential.


    Hazards (top)

    The following is an overview of the hazards to be avoided when handling and storing compressed gases:

    • Asphyxiation: Simple asphyxiation is the primary hazard associated with inert gases. Because inert gases are colorless and odorless, they can escape into the atmosphere undetected and quickly reduce the concentration of oxygen below the level necessary to support life. The use of oxygen monitoring equipment is strongly recommended for enclosed areas where inert gases are being used.
    • Fire and Explosion: Fire and explosion are the primary hazards associated with flammable gases, oxygen and other oxidizing gases. Flammable gases can be ignited by static electricity or by a heat source, such as a flame or a hot object. Oxygen and other oxidizing gases do not burn, but will support combustion of organic materials. Increasing the concentration of an oxidizer accelerates the rate of combustion. Materials that are nonflammable under normal conditions may burn in an oxygen-enriched atmosphere.
    • Chemical Burns: Corrosive gases can chemically attack various materials, including fire-resistant clothing. Some gases are not corrosive in their pure form, but can become extremely destructive if a small amount of moisture is added. Corrosive gases can cause rapid destruction of skin and eye tissue.
    • Chemical Poisoning: Chemical poisoning is the primary hazard of toxic gases. Even in very small concentrations, brief exposure to these gases can result in serious poisoning injuries. Symptoms of exposure may be delayed.
    • High Pressure: All compressed gases are potentially hazardous because of the high pressure stored inside the cylinder. A sudden release of pressure can cause injuries and property damage by propelling a cylinder or whipping a line.
    • Cylinder Weight: A full size cylinder may weigh more than 130 pounds. Moving a cylinder manually may lead to back or muscle injury. Dropping or dragging a cylinder could cause serious injury.


    Handling Precautions (top)

    Cylinder Stand

    • Avoid dropping, dragging or sliding cylinders. Use a suitable hand truck or cart equipped with a chain or belt for securing the cylinder to the cart, even for short distances.
    • Do not permit cylinders to strike each other violently. Cylinders should not be used as rollers for moving material or other equipment.
    • Cylinder caps should be left on each cylinder until it has been secured against a wall or bench or placed in a cylinder stand, and is ready for installation of the regulator. Cylinder caps protect the valve on top of the cylinder from damage if knocked.
    • Never tamper with pressure relief devices in valves or cylinders.
    • Use only wrenches or tools provided by the cylinder supplier to remove a cylinder cap or to open a valve. Never use a screwdriver or pliers.
    • Keep the cylinder valve closed except when in use.
    • Position cylinders so that the cylinder valve is accessible at all times.
    • Use compressed gases only in a well-ventilated area. Toxic, flammable and corrosive gases should be carefully handled in a hood or gas cabinet. Proper containment systems should be used and minimum quantities of these products should be kept on-site.
    • When discharging gas into a liquid, a trap or suitable check valve should be used to prevent liquid from getting back into the cylinder or regulator.
    • Where more than one type of gas is in use, label gas lines. This is particularly important when the gas supply is not in the same room or area as the operation using the gases.
    • Do not use the cylinder valve itself to control flow by adjusting the pressure.


    Storage of Compressed Gas Cylinders (top)

    • All cylinders must be secured to a wall, bench or fixed support using a chain or strap placed 2/3 of the way up. Cylinder stands are an alternative to straps.
    • Cylinders should be strapped individually.
    • Cylinders should not be stored with a regulator attached. Secure the proper gas cap to the threaded portion on the top of the cylinder to protect the valve.*
    • Do not store full and empty cylinders together.
    • Oxidizers and flammable gases should be stored in areas separated by at least 20 feet or by a noncombustible wall.
    • Cylinders should not be stored near radiators or other heat sources. If storage is outdoors, protect cylinders from weather extremes and damp ground to prevent corrosion.
    • No part of a cylinder should be subjected to a temperature higher than 125oF. A flame should never be permitted to come in contact with any part of a compressed gas cylinder.
    • Do not place cylinders where they may become part of an electric circuit.
    • Keep the number of cylinders in a laboratory to a minimum to reduce the fire and toxicity hazards.
    • Lecture bottles should always be returned to the distributor or manufacturer promptly when no longer needed or discarded if at atmospheric pressure.
    • Ensure that the cylinder is properly and prominently labeled as to its contents.
    • NEVER place acetylene cylinders on their side.

    *Air Liquide offers a new type of valve protection device that remains permanently attached and still allows access to the main valve. See Air Liquide for more information.


    Using Compressed Gas Cylinders (top)

    Pressure Regulator

    Before using cylinders, read all label information and safety data sheets (SDSs) associated with the gas being used. The cylinder valve outlet connections are designed to prevent mixing of incompatible gases. The outlet threads vary in diameter; some are internal and some are external; some are right-handed and some are left-handed. Generally, right-handed threads are used for fuel gases.

    To set up and use the cylinder, follow these steps:

    1. Attach the closed regulator to the cylinder. Never open the cylinder valve unless the regulator is completely closed. Regulators are specific to the gas involved. A regulator should be attached to a cylinder without forcing the threads. Ensure the threads of both the regulator and main valve are clean. If the inlet of a regulator does not fit the cylinder outlet, no effort should be made to try to force the fitting. A poor fit may indicate that the regulator is not intended for use on the gas chosen.
    2. Turn the delivery pressure adjusting screw counter-clockwise until it turns freely. This prevents unintended gas flow into the regulator.
    3. Open the cylinder slowly until the inlet gauge on the regulator registers the cylinder pressure. If the cylinder pressure reading is lower than expected, the cylinder valve may be leaking.
    4. With the flow control valve at the regulator outlet closed, turn the delivery pressure adjusting screw clockwise until the required delivery pressure is reached.
    5. Check for leaks using Snoop or soap solution. At or below freezing temperatures, use a glycerin and water solution, such as Snoop, rather than soap. Never use an open flame to detect leaks.
    6. When finished with the gas, close the cylinder valve, release the regulator pressure and replace the gas cap if it will not be used in the near future.


    Assembly of Equipment and Piping (top)

    • Do not force threads that do not fit exactly.
    • Use Teflon tape or thread lubricant for assembly. Teflon tape should only be used for tapered pipe thread, not straight lines or metal-to-metal contacts.
    • Avoid sharp bends of copper tubing. Copper tubing hardens and cracks with repeated bending.
    • Inspect tubing frequently and replace when necessary.
    • Tygon and plastic tubing are not appropriate for most pressure work. These materials can fail under pressure or thermal stress.
    • Do not mix different brands and types of tube fittings. Construction parts are usually not interchangeable.
    • Do not use oil or lubricants on equipment used with oxygen.
    • Do not use copper piping for acetylene.
    • Do not use cast iron piping for chlorine.


    Leaking Cylinders (top)

    Most leaks occur at the valve in the top of the cylinder and may involve the valve threads valve stem, valve outlet, or pressure relief devices. Lab personnel should not attempt to repair leaking cylinders.

    Where action can be taken without serious exposure to lab personnel:

    1. Move the cylinder to an isolated, well-ventilated area (away from combustible materials if the cylinder contains a flammable or oxidizing gas).
    2. Contact Public Safety at 911 or EHS at (609) 258-5294.

    Whenever a large or uncontrollable leak occurs, evacuate the area and immediately contact Public Safety at 911 or EHS at (609) 258-5294.


    Empty Cylinders (top)

    • Remove the regulator and replace the cylinder cap.
    • Mark the cylinder as "empty" or "MT" and store in a designated area for return to the supplier.
    • Do not store full and empty cylinders together.
    • Do not have full and empty cylinders connected to the same manifold. Reverse flow can occur when an empty cylinder is attached to a pressurized system.
    • Do not refill empty cylinders. Only the cylinder supplier should refill gases.
    • Do not empty cylinders to a pressure below 25 psi (172 Kpa). The residual contents may become contaminated with air.
    • Lecture bottles should always be returned to the distributor or manufacturer promptly when no longer needed. Do not purchase lecture bottles that cannot be returned.


    Flammable Gases (top)

    • Keep sources of ignition away from the cylinders.
    • Oxidizers and flammable gases should be stored in areas separated by at least 20 feet or by a non-combustible wall.
    • Bond and ground all cylinders, lines and equipment used with flammable compressed gases.


    Highly Toxic Gases (top)

    Highly toxic gases, such as arsine, boron trifluoride, diborane, ethylene oxide, fluorine, germane, hydrogen cyanide, phosgene, and silane, can pose a significant health risk in the event of a leak. Use of these materials requires written approval by the Principal Investigator or supervisor, using the Particularly Hazardous Substances Use Approval form.

    The following additional precautions must be taken:

    • Use and store in a specially ventilated gas cabinet or fume hood.
    • Use coaxial (double walled) tubing with nitrogen between the walls for feed lines operating above atmospheric pressure.
    • Regulators should be equipped with an automatic shut-off to turn off gas supply in the event of sudden loss of pressure in the supply line.
    • An alarm system should be installed to check for leaks in routinely used gases with poor warning properties. The alarm level must be set at or lower than the permissible exposure limit of the substance.
    • Self-contained breathing apparatus (SCBA) may be appropriate for changing cylinders of highly toxic gases. Use of an SCBA requires enrollment in the Respiratory Protection Program and annual training and fit-testing.
    • Ensure storage and use areas are posted with Designated Area signage.


    Gases Requiring Special Handling (top)

    The following gases present special hazards either due to their toxicity or physical properties. Review this information before using these gases.


    Appendix E: Best Practices in Laboratory Safety Management

    Appendix E: Best Practices in Laboratory Safety Management

    Annual Department Safety Orientation and Quiz (top)

    Chemical Engineering has instituted very effective safety orientation programs. It includes a presentation by the Chemical Hygiene Officer, Public Safet and EHS about safety in their department, where to find information, emergency procedures, etc. This is followed by a quiz that tests the knowledge of the information presented.

    Safety Resource Centers (top)

    Chemical Engineering, PRISM, Electrical Engineering and CEE have established safety resource areas. In Chemical Engineering, this involves a safety information bulletin board and an area of the lounge. In CEE, it includes a locked cabinet, with keys posted in each laboratory. In Electrical Engineering, it includes a shelving unit. These areas include material safety data sheet collections, Chemical Hygiene Plans, other safety publications, forms, waste stickers, spill control materials and more.

    Professor Sherer in CEE has also established a safety drawer for each laboratory. This drawer holds extra safety glasses, gloves, a flash light and other safety equipment.

    Departmental Safety Committees

    Chemical Engineering, Chemistry, Electrical Engineering, MAE, Physics, and CEE have effective safety committees that include faculty, staff and graduate students. EEB is beginning such a committee this year. Molecular Biology has an organization of laboratory managers that meet regularly and discuss safety issues along with other agenda items.

    Graduate Student Training

    The School of Engineering, Molecular Biology, Chemistry and Physics have established training programs for incoming graduate students. For Chemistry and Molecular Biology, training is given as part of the orientation during the first weeks of school, before classes begin. For SEAS, training is given as a series of one hour seminars during lunch time. Beginning this year, virtually all departments will offer department-specific laboratory safety training, given by EHS, every fall.

    Undergraduate Safety Training

    Chemistry, Molecular Biology and Chemical Engineering have established training programs for undergraduates. All are conducted as part of the core laboratory and are considered part of the curriculum. MAE has suggested mandatory training for all SEAS undergrads.

    Professor Royce in MAE developed a computer-based laboratory notebook with safety considerations and procedures for use by undergraduates in his laboratory.

    Orientation of New Faculty and Staff

    The Department Safety Manager in Molecular Biology meets with all new personnel to give them the keys to their laboratory and other assigned areas. During that time, he reviews safety policies and explains where to find additional resources for health and safety issues.

    Molecular Biology has an orientation program for new lab managers. Part of the orientation includes an explanation of the various safety programs and the lab manager's responsibility for safety in the laboratory.

    Laboratory Checkout Procedures

    Chemical Engineering, Chemistry and CEE have established checkout procedures for departing faculty, staff and students. This program is meant to ensure that all chemicals are labeled and wastes removed before a person leaves the university.

    Safety Information Postings

    • Chemical Engineering, Chemistry and CEE have safety information bulletin boards outside the main office.
    • Physics posts safety information in the elevators.
    • Chemical Engineering developed an emergency information and evaluation poster that is placed inside the door to each laboratory area.
    • Professor Hecht's laboratory in Chemistry has waste procedures posted in the laboratory.
    • Professor Shenks' laboratory has outstanding signage posted to aid in properly labeling chemical waste containers. This includes a poster with samples of correctly completed labels for its regular waste streams.
    • Chemistry has specially made holders for Emergency Information Posters outside each laboratory and chemical storage area.
    • MAE machine shop and SEAS machine shop post Shop Rules
    • CEE has MSDS holders outside the entrance to each laboratory.
    • EEB posts an EHS directory, established by EEB from information on the EHS web page, posted in each laboratory.

    Performance Appraisals (top)

    Psychology and Physics include safety as part of their performance appraisals.

    Safety Policies (top)

    The School of Engineering has an extensive safety policy that is distributed to all personnel each fall, along with a letter from the Associate Dean explaining that everyone is expected to read, understand and comply with the policy.

    Laboratory Inspections

    In addition to the limited laboratory inspections conducted annually by EHS technical staff, all SEAS departments conduct their own internal inspections at least annually. Chemical Engineering involves their safety committee.

    Laboratory Practices (top)

    • Professor Sherer's (CEE) laboratory serves as an excellent example for proper chemical segregation and storage.
    • The laboratories in PRISM using highly toxic gases have excellent gas cabinets and specialized monitoring systems.
    • The clean rooms in PRISM and Electrical Engineering are well designed.
    • Physics has an effective program in place for regular inspection of hoisting and rigging equipment.
    • The Molecular Biology 214 lab instructors have modified laboratory procedures to significantly reduce the use of hazardous materials and production of hazardous waste. The use of acrylamide has been completely eliminated.
    • The SEAS machine shop emphasizes and enforces the use of personal protective equipment by keeping a supply of safety glasses at the entrance and by having several safety glasses cleaning stations set up around the shop.

    Laser Laboratory Practices (top)

    • Professor Prucnal's laboratory in Electrical Engineering uses fiber optics to enclose the laser beam and still be able to direct the beam however needed.
    • Professor Austin's laser facility in Physics is well designed, labeled and posted with operating procedures.
    • Professor Scoles developed a simple means for storing tools off the laser table, out of the way of the laser beam.


    Appendix D: Health and Safety Design Considerations for Laboratories »

    Section 7F: Cryogenics

    SECTION 7: Safe Lab Practices and Procedures


    Cryogenic liquids have boiling points less than -73ºC (-100ºF). Liquid nitrogen, liquid oxygen and carbon dioxide are the most common cryogenic materials used in the laboratory. Hazards may include fire, explosion, embrittlement, pressure buildup, frostbite and asphyxiation.

    Many of the safety precautions observed for compressed gases also apply to cryogenic liquids. Two additional hazards are created from the unique properties of cryogenic liquids:

    • Extremely Low Temperatures –The cold boil-off vapor of cryogenic liquids rapidly freezes human tissue. Most metals become stronger upon exposure to cold temperatures, but materials such as carbon steel, plastics and rubber become brittle or even fracture under stress at these temperatures. Proper material selection is important. Cold burns and frostbite caused by cryogenic liquids can result in extensive tissue damage.
    • Vaporization - All cryogenic liquids produce large volumes of gas when they vaporize. Liquid nitrogen will expand 696 times as it vaporizes. The expansion ratio of argon is 847:1, hydrogen is 851:1 and oxygen is 862:1. If these liquids vaporize in a sealed container, they can produce enormous pressures that could rupture the vessel. (See Anecdotes for an account of such an incident.) For this reason, pressurized cryogenic containers are usually protected with multiple pressure relief devices.

    Vaporization of cryogenic liquids (except oxygen) in an enclosed area can cause asphyxiation. Vaporization of liquid oxygen can produce an oxygen-rich atmosphere, which will support and accelerate the combustion of other materials. Vaporization of liquid hydrogen can form an extremely flammable mixture with air.


    Handling Cryogenic Liquids (top)

    Most cryogenic liquids are odorless, colorless, and tasteless when vaporized. When cryogenic liquids are exposed to the atmosphere, the cold boil-off gases condense the moisture in the air, creating a highly visible fog.

    • Always handle these liquids carefully to avoid skin burns and frostbite. Exposure that may be too brief to affect the skin of the face or hands may damage delicate tissues, such as the eyes.
    • Boiling and splashing always occur when charging or filling a warm container with cryogenic liquid or when inserting objects into these liquids. Perform these tasks slowly to minimize boiling and splashing. Use tongs to withdraw objects immersed in a cryogenic liquid.
    • Never touch uninsulated pipes or vessels containing cryogenic liquids. Flesh will stick to extremely cold materials. Even nonmetallic materials are dangerous to touch at low temperatures.
    • Use wooden or rubber tongs to remove small items from cryogenic liquid baths. Cryogenic gloves are for indirect or splash protection only, they are not designed to protect against immersion into cryogenic liquids.
    • Cylinders and dewars should not be filled to more than 80% of capacity, since expansion of gases during warming may cause excessive pressure buildup.
    • Check cold baths frequently to ensure they are not plugged with frozen material.


    Protective Clothing (top)

    Face shields worn with safety glasses or chemical splash goggles are recommended during transfer and handling of cryogenic liquids.

    Wear loose fitting, dry, insulated cryogenic gloves when handling objects that come into contact with cryogenic liquids and vapor. Trousers should be worn on the outside of boots or work shoes.


    Cooling Baths and Dry Ice (top)

    • Neither liquid nitrogen nor liquid air should be used to cool a flammable mixture in the presence of air, because oxygen can condense from the air, leading to an explosion hazard.
    • Wear insulated, dry gloves and a face shield when handling dry ice.
    • Add dry ice slowly to the liquid portion of the cooling bath to avoid foaming over. Do not lower your head into a dry ice chest, since suffocation can result from carbon dioxide buildup.


    Liquid Nitrogen Cooled Traps (top)

    Traps that open to the atmosphere condense liquid air rapidly. If you close the system, pressure builds up with enough force to shatter glass equipment. Therefore, only sealed or evacuated equipment should use liquid nitrogen cooled traps.

    Section 7G: Electrical Safety

    SECTION 7: Safe Work Practices and Procedures


    Electrically powered equipment, such as hot plates, stirrers, vacuum pumps, electrophoresis apparatus, lasers, heating mantles, ultrasonicators, power supplies, and microwave ovens are essential elements of many laboratories. These devices can pose a significant hazard to laboratory workers, particularly when mishandled or not maintained. Many laboratory electrical devices have high voltage or high power requirements, carrying even more risk. Large capacitors found in many laser flash lamps and other systems are capable of storing lethal amounts of electrical energy and pose a serious danger even if the power source has been disconnected.

    Accounts of incidents on campus that resulted in electrical shock, including a near fatal incident, are described in Anecdotes.


    Electrical Hazards (top)


    The major hazards associated with electricity are electrical shock and fire. Electrical shock occurs when the body becomes part of the electric circuit, either when an individual comes in contact with both wires of an electrical circuit, one wire of an energized circuit and the ground, or a metallic part that has become energized by contact with an electrical conductor.

    The severity and effects of an electrical shock depend on a number of factors, such as the pathway through the body, the amount of current, the length of time of the exposure, and whether the skin is wet or dry. Water is a great conductor of electricity, allowing current to flow more easily in wet conditions and through wet skin. The effect of the shock may range from a slight tingle to severe burns to cardiac arrest. The chart below shows the general relationship between the degree of injury and amount of current for a 60-cycle hand-to-foot path of one second's duration of shock. While reading this chart, keep in mind that most electrical circuits can provide, under normal conditions, up to 20,000 milliamperes of current flow

    Current Reaction
    1 Milliampere Perception level
    5 Milliamperes Slight shock felt; not painful but disturbing
    6-30 Milliamperes Painful shock; "let-go" range
    50-150 Milliamperes Extreme pain, respiratory arrest, severe muscular contraction
    1000-4,300 Milliamperes Ventricular fibrillation
    10,000+ Milliamperes Cardiac arrest, severe burns and probable death

    In addition to the electrical shock hazards, sparks from electrical equipment can serve as an ignition source for flammable or explosive vapors or combustible materials. See Anecdotes.

    Power Loss

    Loss of electrical power can create hazardous situations. Flammable or toxic vapors may be released as a chemical warms when a refrigerator or freezer fails. Fume hoods may cease to operate, allowing vapors to be released into the laboratory. If magnetic or mechanical stirrers fail to operate, safe mixing of reagents may be compromised.


    Preventing Electrical Hazards (top)

    There are various ways of protecting people from the hazards caused by electricity, including insulation, guarding, grounding, and electrical protective devices. Laboratory workers can significantly reduce electrical hazards by following some basic precautions:

    • Inspect wiring of equipment before each use. Replace damaged or frayed electrical cords immediately.
    • Use safe work practices every time electrical equipment is used.
    • Know the location and how to operate shut-off switches and/or circuit breaker panels. Use these devices to shut off equipment in the event of a fire or electrocution.
    • Limit the use of extension cords. Use only for temporary operations and then only for short periods of time. In all other cases, request installation of a new electrical outlet.
    • Multi-plug adapters must have circuit breakers or fuses.
    • Place exposed electrical conductors (such as those sometimes used with electrophoresis devices) behind shields.
    • Minimize the potential for water or chemical spills on or near electrical equipment.


    All electrical cords should have sufficient insulation to prevent direct contact with wires. In a laboratory, it is particularly important to check all cords before each use, since corrosive chemicals or solvents may erode the insulation.

    Damaged cords should be repaired or taken out of service immediately, especially in wet environments such as cold rooms and near water baths.


    Live parts of electric equipment operating at 50 volts or more (i.e., electrophoresis devices) must be guarded against accidental contact. Plexiglas shields may be used to protect against exposed live parts.



    Only equipment with three-prong plugs should be used in the laboratory. The third prong provides a path to ground for internal electrical short circuits, thereby protecting the user from a potential electrical shock.

    Circuit Protection Devices

    Circuit protection devices are designed to automatically limit or shut off the flow of electricity in the event of a ground-fault, overload or short circuit in the wiring system. Ground-fault circuit interrupters, circuit breakers and fuses are three well-known examples of such devices.

    Fuses and circuit breakers prevent over-heating of wires and components that might otherwise create fire hazards. They disconnect the circuit when it becomes overloaded. This overload protection is very useful for equipment that is left on for extended periods of time, such as stirrers, vacuum pumps, drying ovens, Variacs and other electrical equipment.

    The ground-fault circuit interrupter, or GFCI, is designed to shutoff electric power if a ground fault is detected, protecting the user from a potential electrical shock. The GFCI is particularly useful near sinks and wet locations. Since GFCIs can cause equipment to shutdown unexpectedly, they may not be appropriate for certain apparatus. Portable GFCI adapters (available in most safety supply catalogs) may be used with a non-GFCI outlet.


    In laboratories where volatile flammable materials are used, motor-driven electrical equipment should be equipped with non-sparking induction motors or air motors. These motors must meet National Electric Safety Code (US DOC, 1993) Class 1, Division 2, Group C-D explosion resistance specifications. Many stirrers, Variacs, outlet strips, ovens, heat tape, hot plates and heat guns do not conform to these code requirements.

    Avoid series-wound motors, such as those generally found in some vacuum pumps, rotary evaporators and stirrers. Series-wound motors are also usually found in household appliances such as blenders, mixers, vacuum cleaners and power drills. These appliances should not be used unless flammable vapors are adequately controlled.

    Although some newer equipment have spark-free induction motors, the on-off switches and speed controls may be able to produce a spark when they are adjusted because they have exposed contacts. One solution is to remove any switches located on the device and insert a switch on the cord near the plug end.


    Safe Work Practices (top)

    The following practices may reduce risk of injury or fire when working with electrical equipment:

    • Avoid contact with energized electrical circuits.
    • Use guarding around exposed circuits and sources of live electricity.
    • Disconnect the power source before servicing or repairing electrical equipment.
    • When it is necessary to handle equipment that is plugged in, be sure hands are dry and, when possible, wear nonconductive gloves and shoes with insulated soles.
    • If it is safe to do so, work with only one hand, keeping the other hand at your side or in your pocket, away from all conductive material. This precaution reduces the likelihood of accidents that result in current passing through the chest cavity.
    • Minimize the use of electrical equipment in cold rooms or other areas where condensation is likely. If equipment must be used in such areas, mount the equipment on a wall or vertical panel.
    • If water or a chemical is spilled onto equipment, shut off power at the main switch or circuit breaker and unplug the equipment.
    • If an individual comes in contact with a live electrical conductor, do not touch the equipment, cord or person. Disconnect the power source from the circuit breaker or pull out the plug using a leather belt.


    High Voltage or Current (top)

    Repairs of high voltage or high current equipment should be performed only by trained electricians. Laboratory workers who are experienced in such tasks and would like to perform such work on their own laboratory equipment must first receive specialized electrical safety related work practices training by EHS staff. Contact the University Safety Engineer at 258-5294 for more information.


    Altering Building Wiring and Utilities (top)

    Any modifications to existing electrical service in a laboratory or building must be completed or approved by either the building facility manager, an engineer from the Facilities department or the building's Special Facilities staff. All modifications must meet both safety standards and Facilities Engineering design requirements.

    Any unapproved laboratory facilities modifications discovered during laboratory surveys or other activities are reviewed by EHS and facility staff to determine whether they meet design specifications.

    Section 7H: Pressure and Vacuum Systems

    SECTION 7: Safe Work Practices and Procedures

    Section 7H: Pressure and Vacuum Systems

    Working with hazardous chemicals at high or low pressures requires planning and special precautions. Procedures should be implemented to protect against explosion or implosion through appropriate equipment selection and the use of safety shields. Care should be taken to select glass apparatus that can safely withstand designated pressure extremes.

    High Pressure Vessels (top)

    • High-pressure operations should be performed only in pressure vessels appropriately selected for the operation, properly labeled and installed, and protected by pressure-relief and necessary control devices.
    • Vessels must be strong enough to withstand the stresses encountered at the intended operating temperatures and pressures and must not corrode or otherwise react when in contact with the materials it contains.
    • Systems designed for use at elevated temperatures should be equipped with a positive temperature controller. Manual temperature control using a simple variable autotransformer, such as a Variac, should be avoided. The use of a back-up temperature controller capable of shutting the system down is strongly recommended.
    • All pressure equipment should be inspected and tested at intervals determined by the severity of the equipment's usage. Visual inspections should be accomplished before each use.
    • Hydrostatic testing should be accomplished before equipment is placed in initial service. Hydrostatic testing should be re-accomplished every ten years thereafter, after significant repair or modification, or if the vessel experiences overpressure or overtemperature. Contact the University Safety Engineer at 258-5294 for more information about hydrostatic testing.

    Vacuum Apparatus (top)

    Vacuum work can result in an implosion and the possible hazards of flying glass, splattering chemicals and fire. All vacuum operations must be set up and operated with careful consideration of the potential risks. Equipment at reduced pressure is especially prone to rapid pressure. Such conditions can force liquids through an apparatus, sometimes with undesirable consequences.

    • Personal protective equipment, such as safety glasses or chemical goggles, face shields, and/or an explosion shield should be used to protect against the hazards of vacuum procedures, and the procedure should be carried out inside a hood.
    • Do not allow water, solvents and corrosive gases to be drawn into vacuum systems. Protect pumps with cold traps and vent their exhaust into an exhaust hood.
    • Assemble vacuum apparatus in a manner that avoids strain, particularly to the neck of the flask.
    • Avoid putting pressure on a vacuum line to prevent stopcocks from popping out or glass apparatus from exploding.
    • Place vacuum apparatus in such a way that the possibility of being accidentally hit is minimized. If necessary, place transparent plastic around it to prevent injury from flying glass in case of an explosion.
    • When possible, avoid using mechanical vacuum pumps for distillation or concentration operations using large quantities of volatile materials. A water aspirator or steam aspirator is preferred. This is particularly important when large quantities of volatile materials are involved.

    Vacuum Trapping

    When using a vacuum source, it is important to place a trap between the experimental apparatus and the vacuum source.  The vacuum trap

    • protects the pump and the piping from the potentially damaging effects of the material
    • protects people who must work on the vacuum lines or system, and
    • prevents vapors and related odors from being emitted back into the laboratory or system exhaust.

    There have been incidents at Princeton where improper trapping caused vapor to be emitted from the exhaust of the house vacuum system, resulting in either re-entry into the
    building or potential exposure to maintenance workers.  Unfortunately, this type of incident is not the worst that can happen.  In 2001, at the University of California -
    Davis, two plumbers were injured when a house vacuum line burst after one of the plumbers attempted to solder a fitting on the copper line.  Results of analysis found
    evidence of copper perchlorate (an oxidizer) and acetate, which created an explosive mixture upon heating by the torch.

    Proper Trapping Techniques
    To prevent contamination, all lines leading from experimental apparatus to the vacuum source should be equipped with filtration or other trapping as appropriate.

    • For particulates, use filtration capable of efficiently trapping the particles in the size range being generated
    • For most aqueous or non-volatile liquids, a filter flask at room temperature is adequate to prevent liquids from getting to the vacuum source.
    • For solvents and other volatile liquids, use a cold trap of sufficient size and cold enough to condense vapors generated, followed by a filter flask capable of collecting fluid that could be aspirated out of the cold trap.
    • For highly reactive, corrosive or toxic gases, use a sorbent canister or scrubbing device capable of trapping the gas.

    Cold Traps
    For most volatile liquids, a cold trap using a slush of dry ice and either isopropanol or ethanol is sufficient (to -78 deg. C).  Avoid using acetone.  Ethanol and isopropanol
    are cheaper and less likely to foam.

    Liquid nitrogen may only be used with sealed or evacuated equipment, and then only with extreme caution.  If the system is opened while the cooling bath is still in contact
    with the trap, oxygen may condense from the atmosphere and react vigorously with any organic material present.

    Glass Vessels (top)

    Although glass vessels are frequently used in pressure and vacuum systems, they can explode or implode violently, either spontaneously from stress failure or from an accidental blow. See Anecdotes for descriptions of some of these incidents.

    • Conduct pressure and vacuum operations in glass vessels behind adequate shielding.
    • Ensure the glass vessel is designed for the intended operation.
    • Carefully check glass vessels for star cracks, scratches or etching marks before each use. Cracks can increase the likelihood of breakage or may allow chemicals to leak into the vessel.
    • Seal glass centrifuge tubes with rubber stoppers clamped in place. Wrap the vessel with friction tape and shield with a metal screen. Alternatively, wrap with friction tape and surround the vessel with multiple layers of loose cloth, then clamp behind a safety shield.
    • Glass tubes with high-pressure sealers should be no more than 3/4 full.
    • Sealed bottles and tubes of flammable materials should be wrapped in cloth, placed behind a safety shield, then cooled slowly, first with an ice bath, then with dry ice.
    • Never rely on corks, rubber stoppers or plastic tubing as pressure-relief devices.
    • Glass vacuum dessicators should be made of Pyrex or similar glass and wrapped partially with friction tape to guard against flying glass. Plastic dessicators are a good alternative to glass, but still require shielding.
    • Never carry or move an evacuated dessicator.

    Dewar Flasks (top)

    Dewar flasks are under vacuum to provide insulation and can collapse from thermal shock or slight mechanical shock.

    • Shield flasks with friction tape or enclose in a wooden or metal container to reduce the risk of flying glass.
    • Use metal flasks if there is a significant possibility of breakage.
    • Styrofoam buckets offer a short-term alternative to dewar flasks.

    Rotovaps (top)

    Rotovaps can implode under certain conditions. Since some Rotovaps contain components made of glass, this can be a serious hazard. See Rotary Evaporators for more information about their safe handling.

    Section 7I: Laboratory Equipment
    Section 7G: Electrical Safety

    Section 7I: Laboratory Equipment

    Section 7: Safe Work Practices and Procedures

    7I: Laboratory Equipment

    Refrigerators and Freezers (top)

    The potential hazards posed by laboratory refrigerators and freezers involve vapors from the contents, the possible presence of incompatible chemicals and spillage.

    Only refrigerators and freezers specified for laboratory use should be utilized for the storage of chemicals. These refrigerators have been constructed with special design factors, such as heavy-duty cords and corrosion resistant interiors to help reduce the risk of fire or explosions in the lab.

    Standard refrigerators have electrical fans and motors that make them potential ignition sources for flammable vapors. Do not store flammable liquids in a refrigerator unless it is approved for such storage. Flammable liquid-approved refrigerators are designed with spark-producing parts on the outside to avoid accidental ignition. If refrigeration is needed inside a flammable-storage room, you should use an explosion-proof refrigerator. 

    Frost-free refrigerators should also be avoided. Many of them have a drain or tube or hole that carries water and possibly any spilled materials to an area near the compression, which may spark. Electric heaters used to defrost the freezing coils can also spark. 

    Only chemicals should be stored in chemical storage refrigerators; lab refrigerators should not be used for food storage or preparation. Refrigerators should be labeled for their intended purpose; labels reading “No Food or Drink to be Stored in this Refrigerator” or “Refrigerator For Food Only” are available from EHS by calling 8-5294. 

    All materials in refrigerators or freezers should be labeled with the contents, owner, date of acquisition or preparation and nature of any potential hazard. Since refrigerators are often used for storage of large quantities of small vials and test tubes, a reference to a list outside of the refrigerator could be used. Labels and ink used to identify materials in the refrigerators should be water-resistant. 

    All containers should be sealed, preferably with a cap. Containers should be placed in secondary containers, or catch pans should be used. 

    Loss of electrical power can produce extremely hazardous situations. Flammable or toxic vapors may be released from refrigerators and freezers as chemicals warm up and/or certain reactive materials may decompose energetically upon warming.  Proactive planning can avoid product loss and hazardous situations in event of an extended power outage. Dry ice or alternate power sources can be used to prevent refrigerator and freezer contents from warming.

    Stirring and Mixing Devices (top)

    The stirring and mixing devices commonly found in laboratories include stirring motors, magnetic stirrers, shakers, small pumps for fluids and rotary evaporators for solvent removal. These devices are typically used in laboratory operations that are performed in a hood, and it is important that they be operated in a way that precludes the generation of electrical sparks.

    Only spark-free induction motors should be used in power stirring and mixing devices or any other rotating equipment used for laboratory operations. While the motors in most of the currently marketed stirring and mixing devices meet this criterion, their on-off switches and rheostat-type speed controls can produce an electrical spark because they have exposed electrical conductors. The speed of an induction motor operating under a load should not be controlled by a variable autotransformer. 

    Because stirring and mixing devices, especially stirring motors and magnetic stirrers, are often operated for fairly long periods without constant attention, the consequences of stirrer failure, electrical overload or blockage of the motion of the stirring impeller should be considered.

    Heating Devices (top)

    Most labs use at least one type of heating device, such as ovens, hot plates, heating mantles and tapes, oil baths, salt baths, sand baths, air baths, hot-tube furnaces, hot-air guns and microwave ovens. Steam-heated devices are generally preferred whenever temperatures of 100o C or less are required because they do not present shock or spark risks and can be left unattended with assurance that their temperature will never exceed 100o C. Ensure the supply of water for steam generation is sufficient prior to leaving the reaction for any extended period of time.

    A number of general precautions need to be taken when working with heating devices in the laboratory. When working with heating devices, consider the following: 

    • The actual heating element in any laboratory heating device should be enclosed in such a fashion as to prevent a laboratory worker or any metallic conductor from accidentally touching the wire carrying the electric current. 
    • Heating device becomes so worn or damaged that its heating element is exposed, the device should be either discarded or repaired before it is used again. 
    • Laboratory heating devices should be used with a variable autotransformer to control the input voltage by supplying some fraction of the total line voltage, typically 110 V.
    • The external cases of all variable autotransformers have perforations for cooling by ventilation and, therefore, should be located where water and other chemicals cannot be spilled onto them and where they will not be exposed to flammable liquids or vapors. 

    Fail-safe devices can prevent fires or explosions that may arise if the temperature of a reaction increases significantly because of a change in line voltage, the accidental loss of reaction solvent or loss of cooling. Some devices will turn off the electric power if the temperature of the heating device exceeds some preset limit or if the flow of cooling water through a condenser is stopped owing to the loss of water pressure or loosening of the water supply hose to a condenser. 


    Electrically heated ovens are commonly used in the laboratory to remove water or other solvents from chemical samples and to dry laboratory glassware. Never use laboratory ovens for human food preparation.

    • Laboratory ovens should be constructed such that their heating elements and their temperature controls are physically separated from their interior atmospheres.
    • Laboratory ovens rarely have a provision for preventing the discharge of the substances volatilized in them. Connecting the oven vent directly to an exhaust system can reduce the possibility of substances escaping into the lab or an explosive concentration developing within the oven. 
    • Ovens should not be used to dry any chemical sample that might pose a hazard because of acute or chronic toxicity unless special precautions have been taken to ensure continuous venting of the atmosphere inside the oven. 
    • To avoid explosion, glassware that has been rinsed with an organic solvent should be rinsed again with distilled water before being dried in an oven.
    • Bimetallic strip thermometers are preferred for monitoring oven temperatures. Mercury thermometers should not be mounted through holes in the top of ovens so that the bulb hangs into the oven. Should a mercury thermometer be broken in an oven of any type, the oven should be closed and turned off immediately, and it should remain closed until cool. All mercury should be removed from the cold oven with the use of appropriate cleaning equipment and procedures in order to avoid mercury exposure.

    Hot Plates

    Laboratory hot plates are normally used for heating solutions to 100o C or above when inherently safer steam baths cannot be used. Any newly purchased hot plates should be designed in a way that avoids electrical sparks. However, many older hot plates pose an electrical spark hazard arising from either the on-off switch located on the hot plate, the bimetallic thermostat used to regulate the temperature or both. Laboratory workers should be warned of the spark hazard associated with older hot plates.

    In addition to the spark hazard, old and corroded bimetallic thermostats in these devices can eventually fuse shut and deliver full, continuous current to a hot plate. 

    • Do not store volatile flammable materials near a hot plate 
    • Limit use of older hot plates for flammable materials. 
    • Check for corrosion of thermostats. Corroded bimetallic thermostats can be repaired or reconfigured to avoid spark hazards. Contact EHS for more info. 

    Heating Mantles

    Heating mantles are commonly used for heating round-bottomed flasks, reaction kettles and related reaction vessels. These mantles enclose a heating element in a series of layers of fiberglass cloth. As long as the fiberglass coating is not worn or broken, and as long as no water or other chemicals are spilled into the mantle, heating mantles pose no shock hazard.

    • Always use a heating mantle with a variable autotransformer to control the input voltage. Never plug them directly into a 110-V line.
    • Be careful not to exceed the input voltage recommended by the mantle manufacturer. Higher voltages will cause it to overheat, melt the fiberglass insulation and expose the bare heating element. 
    • If the heating mantle has an outer metal case that provides physical protection against damage to the fiberglass, it is good practice to ground the outer metal case to protect against an electric shock if the heating element inside the mantle shorts against the metal case. 
    • Some older equipment might have asbestos insulation rather than fiberglass. Contact EHS to replace the insulation and for proper disposal of the asbestos. 

    Oil, Salt and Sand Baths

    Electrically heated oil baths are often used to heat small or irregularly shaped vessels or when a stable heat source that can be maintained at a constant temperature is desired. Molten salt baths, like hot oil baths, offer the advantages of good heat transfer, commonly have a higher operating range (e.g., 200 to 425oC) and may have a high thermal stability (e.g., 540oC).There are several precautions to take when working with these types of heating devices:

    • Take care with hot oil baths not to generate smoke or have the oil burst into flames from overheating.
    • Always monitor oil baths by using a thermometer or other thermal sensing devices to ensure that its temperature does not exceed the flash point of the oil being used. 
    • Fit oil baths left unattended with thermal sensing devices that will turn off the electric power if the bath overheats. 
    • Mix oil baths well to ensure that there are no “hot spots” around the elements that take the surrounding oil to unacceptable temperatures. 
    • Contain heated oil in a vessel that can withstand an accidental strike by a hard object. 
    • Mount baths carefully on a stable horizontal support such as a laboratory jack that can be raised or lowered without danger of the bath tipping over. Iron rings are not acceptable supports for hot baths. 
    • Clamp equipment high enough above a hot bath that if the reaction begins to overheat, the bath can be lowered immediately and replaced with a cooling bath without having to readjust the equipment setup. 
    • Provide secondary containment in the event of a spill of hot oil. 
    • Wear heat-resistant gloves when handling a hot bath. 
    • The reaction container used in a molten salt bath must be able to withstand a very rapid heat-up to a temperature above the melting point of salt. 
    • Take care to keep salt baths dry since they are hygroscopic, which can cause hazardous popping and splattering if the absorbed water vaporizes during heat-up. 

    Hot Air Baths and Tube Furnaces

    Hot air baths are used in the lab as heating devices. Nitrogen is preferred for reactions involving flammable materials. Electrically heated air baths are frequently used to heat small or irregularly shaped vessels. One drawback of the hot air bath is that they have a low heat capacity. As a result, these baths normally have to be heated to 100oC or more above the target temperature. Tube furnaces are often used for high-temperature reactions under pressure. Consider the following when working with either apparatus:

    • Ensure that the heating element is completely enclosed. 
    • For air baths constructed of glass, wrap the vessel with heat resistant tape to contain the glass if it should break. 
    • Sand baths are generally preferable to air baths. 
    • For tube furnaces, carefully select glassware and metal tubes and joints to ensure they are able to withstand the pressure. 
    • Follow safe practices outlined for both electrical safety and pressure and vacuum systems. 

    Heat Guns

    Laboratory heat guns are constructed with a motor-driven fan that blows air over an electrically heated filament. They are frequently used to dry glassware or to heat the upper parts of a distillation apparatus during distillation of high-boiling materials.

    Read the Heat Gun Advisory for more information on proper selection and use of a heat gun for research operations.

    Microwave Ovens

    Microwave ovens used in the laboratory may pose several different types of hazards.

    • As with most electrical apparatus, there is the risk of generating sparks that can ignite flammable vapors.
    • Metals placed inside the microwave oven may produce an arc that can ignite flammable materials.
    • Materials placed inside the oven may overheat and ignite.
    • Sealed containers, even if loosely sealed, can build pressure upon expansion during heating, creating a risk of container rupture.

    To minimize the risk of these hazards, 

    • Never operate microwave ovens with doors open in order to avoid exposure to microwaves.
    • Do not place wires and other objects between the sealing surface and the door on the oven’s front face. The sealing surfaces must be kept absolutely clean.
    • Never use a microwave oven for both laboratory use and food preparation.
    • Electrically ground the microwave. If use of an extension cord is necessary, only a three-wire cord with a rating equal to or greater than that for the oven should be used.
    • Do not use metal containers and metal-containing objects (e.g., stir bars) in the microwave. They can cause arcing.
    • Do not heat sealed containers in the microwave oven. Even heating a container with a loosened cap or lid poses a significant risk since microwave ovens can heat material so quickly that the lid can seat upward against the threads and containers can explode.
    • Remove screw caps from containers being microwaved. If the sterility of the contents must be preserved, use cotton or foam plugs. Otherwise plug the container with kimwipes to reduce splash potential.

    Ultrasonicators (top)

    Human exposure to ultrasound with frequencies between 16 and 100 kilohertz (kHz) can be divided into three distinct categories: airborne conduction, direct contact through a liquid coupling medium, and direct contact with a vibrating solid.

    Ultrasound through airborne conduction does not appear to pose a significant health hazard to humans. However, exposure to the associated high volumes of audible sound can produce a variety of effects, including fatigue, headaches, nausea and tinnitus. When ultrasonic equipment is operated in the laboratory, the apparatus must be enclosed in a 2-cm thick wooden box or in a box lined with acoustically absorbing foam or tiles to substantially reduce acoustic emissions (most of which are inaudible). 

    Direct contact of the body with liquids or solids subjected to high-intensity ultrasound of the sort used to promote chemical reactions should be avoided. Under sonochemical conditions, cavitation is created in liquids, and it can induce high-energy chemistry in liquids and tissues. Cell death from membrane disruption can occur even at relatively low acoustic intensities. 

    Exposure to ultrasonically vibrating solids, such as an acoustic horn, can lead to rapid frictional heating and potentially severe burns. 

    Centrifuges (top)

    Centrifuges should be properly installed and must be operated only by trained personnel. It is important that the load is balanced each time the centrifuge is used and that the lid be closed while the rotor is in motion. The disconnect switch must be working properly to shut off the equipment when the top is opened, and the manufacturer’s instructions for safe operating speeds must be followed.

    For flammable and/or hazardous materials, the centrifuge should be under negative pressure to a suitable exhaust system. 

    Rotary Evaporators (top)

    Glass components of the rotary evaporator should be made of Pyrex or similar glass. Glass vessels should be completely enclosed in a shield to guard against flying glass should the components implode. Increase in rotation speed and application of vacuum to the flask whose solvent is to be evaporated should be gradual.

    Autoclaves (top)

    The use of an autoclave is a very effective way to decontaminate infectious waste. Autoclaves work by killing microbes with superheated steam. The following are recommended guidelines when using an autoclave: 

    • Do not put sharp or pointed contaminated objects into an autoclave bag. Place them in an appropriate rigid sharps disposal container.
    • Use caution when handling an infectious waste autoclave bag, in case sharp objects were inadvertently placed in the bag. Never lift a bag from the bottom to load it into the chamber. Handle the bag from the top. 
    • Do not overfill an autoclave bag. Steam and heat cannot penetrate as easily to the interior of a densely packed autoclave bag. Frequently the outer contents of the bag will be treated but the innermost part will be unaffected. 
    • Do not overload an autoclave. An overpacked autoclave chamber does not allow efficient steam distribution. Considerably longer sterilization times may be required to achieve decontamination if an autoclave is tightly packed. 
    • Conduct autoclave sterility testing on a regular basis using appropriate biological indicators (B. stearothermophilus spore strips) to monitor efficacy. Use indicator tape with each load to verify it has been autoclaved. 
    • Do not mix contaminated and clean items together during the same autoclave cycle. Clean items generally require shorter decontamination times (15-20 minutes) while a bag of infectious waste (24" x 36") typically requires 45 minutes to an hour to be effectively decontaminated throughout. 
    • Always wear personal protective equipment, including heat-resistant gloves, safety glasses and a lab coat when operating an autoclave. Use caution when opening the autoclave door. Allow superheated steam to exit before attempting to remove autoclave contents. 
    • Be on the alert when handling pressurized containers. Superheated liquids may spurt from closed containers. Never seal a liquid container with a cork or stopper. This could cause an explosion inside the autoclave. 
    • Agar plates will melt and the agar will become liquefied when autoclaved. Avoid contact with molten agar. Use a secondary tray to catch any potential leakage from an autoclave bag rather than allowing it to leak onto the floor of the autoclave chamber. 
    • If there is a spill inside the autoclave chamber, allow the unit to cool before attempting to clean up the spill. If glass breaks in the autoclave, use tongs, forceps or other mechanical means to recover fragments. Do not use bare or gloved hands to pick up broken glassware. 
    • Do not to leave an autoclave operating unattended for a long period of time. Always be sure someone is in the vicinity while an autoclave is cycling in case there is a problem. 
    • Autoclaves should be placed under preventive maintenance contracts to ensure they are operating properly. 

    Electrophoresis Devices (top)

    Precautions to prevent electric shock must be followed when conducting procedures involving electrophoresis. Lethal electric shock can result when operating at high voltages such as in DNA sequencing or low voltages such as in agarose gel electrophoresis (e.g., 100 volts at 25 milliamps).These general guidelines should be followed:

    • Turn the power off before connecting the electrical leads 
    • Connect one lead at a time, using one hand only 
    • Ensure that hands are dry while connecting leads 
    • Keep the apparatus away from sinks or other water sources 
    • Turn off power before opening lid or reaching inside chamber 
    • Do not override safety devices 
    • Do not run electrophoresis equipment unattended. 
    • If using acrylamide, purchase premixed solutions or pre-weighed quantities whenever possible 
    • If using ethidium bromide, have a hand-held UV light source available in the laboratory. Check working surfaces after each use. 
    • Mix all stock solutions in a chemical fume hood. 
    • Provide spill containment by mixing gels on a plastic tray 
    • Decontaminate surfaces with ethanol. Dispose of all cleanup materials as hazardous waste. 

    Glassware (top)

    Although glass vessels are frequently used in low-vacuum operations, evacuated glass vessels may collapse violently, either spontaneously from strain or from an accidental blow. Therefore, pressure and vacuum operations in glass vessels should be conducted behind adequate shielding. It is advisable to check for flaws such as star cracks, scratches and etching marks each time a vacuum apparatus is used. Only round-bottomed or thick-walled (e.g., Pyrex) evacuated reaction vessels specifically designed for operations at reduced pressure should be used. Repaired glassware is subject to thermal shock and should be avoided. Thin-walled, Erlenmeyer or round-bottomed flasks larger than 1 L should never be evacuated.

    Vacuums (top)

    Vacuum pumps are used in the lab to remove air and other vapors from a vessel or manifold. The most common usages are on rotary evaporators, drying manifolds, centrifugal concentrators (“speedvacs”), acrylamide gel dryers, freeze dryers, vacuum ovens, tissue culture filter flasks and aspirators, desiccators, filtration apparatus and filter/degassing apparatus.

    The critical factors in vacuum pump selection are:

    • Application the pump will be used on
    • Nature of the sample (air, chemical, moisture)
    • Size of the sample(s)

    When using a vacuum pump on a rotary evaporator, a dry ice alcohol slurry cold trap or a refrigerated trap is recommended. A Cold Trap should be used in line with the pump when high vapor loads from drying samples will occur. Consult manufacturer for specific situations. These recommendations are based on keeping evaporating flask on rotary evaporator at 400 C. Operating at a higher temperature allows the Dry Vacuum System to strip boiling point solvents with acceptable evaporation rates.

    Vacuum pumps can pump vapors from air, water to toxic and corrosive materials like TFA and methylene chloride. Oil seal pumps are susceptible to excessive amounts of solvent, corrosive acids and bases and excessive water vapors. Pump oil can be contaminated quite rapidly by solvent vapors and mists. Condensed solvents will thin the oil and diminish its lubricating poroperties, possibly seizing the pump motor. Corrosives can create sludge by breaking down the oil and cause overheating. Excess water can coagulate the oil and promotes corrosion within the pump. Proper trapping (cold trap, acid trap) and routine oil changes greatly extend the life of an oil seal vacuum. Pump oil should be changed when it begins to turn a dark brown color.

    Diaphragm pumps are virtually impervious to attack from laboratory chemical vapors. They are susceptible to physical wearing of the membrane if excessive chemical vapors are allowed to condense and crystallize in the pumping chambers. A five minute air purge either as part of the procedure or at day’s end will drive off condensed water vapors and further prolong pump life.

    Hazardous chemicals can escape from the vacuum pump and pump should be place in the hood. Cold traps and acid traps can be helpful, but if allowed to thaw or saturate, they can lose their effectiveness.

    Section 7J: Particularly Hazardous Substances
    Section 7H: Pressure and Vacuum Systems

    Section 7J: Particularly Hazardous Substances

    SECTION 7: Safe Work Practices and Procedures

    7J: Particularly Hazardous Substances

    As a matter of good practice, and to satisfy regulatory requirement, particularly hazardous substances require additional planning and considerations.

    A list of particularly hazardous substances is available in Appendix A of this manual. This list is not exhaustive; consult the material safety data sheet to determine whether a particular chemical may be considered a carcinogen, reproductive hazard or substance with a high acute toxicity.

    Definitions (top)

    The OSHA Laboratory Standard defines particularly hazardous substances as:

    • Carcinogens – A carcinogen is a substance capable of causing cancer. Carcinogens are chronically toxic substances; that is, they cause damage after repeated or long-duration exposure, and their effects may become evident only after a long latency period.

    A chemical is considered a carcinogen, for the purpose of the Laboratory Safety Manual, if it is included in any of the following carcinogen lists:

        • OSHA-regulated carcinogens as listed in Subpart Z of the OSHA standards. The current list of substances that OSHA regulates as carcinogens or potential carcinogens follows:
          • asbestos
          • 4-Nitrobiphenyl
          • alpha-Naphthylamine
          • Methyl chloromethyl ether
          • 3,3'-Dichlorobenzidine (and its salts)
          • bis-Chloromethyl ether
          • beta-Naphthylamine
          • Benzidine
          • 4-Aminodiphenyl
          • Ethyleneimine
          • beta-Propiolactone
          • 2-Acetylaminofluorene
          • 4-Dimethylaminoazobenzene
          • N-Nitrosodimethylamine
          • Vinyl chloride
          • Inorganic arsenic
          • Cadmium
          • Benzene
          • Coke oven emissions
          • 1,2-dibromo-3-chloropropane
          • Acrylonitrile
          • Ethylene oxide
          • Formaldehyde
          • Methylenedianiline
          • 1,3-Butadiene
          • Methylene Chloride
        • Under the category "known to be carcinogens" in the Annual Report of Carcinogens published by the National Toxicology Program (NTP) latest edition
        • Group 1 ("carcinogenic to humans") of the International Agency for Research on Cancer (IARC), latest edition. Chemicals listed in Group 2A or 2B ("reasonably anticipated to be carcinogens") that cause significant tumor incidence in experimental animals under specified conditions are also considered carcinogens under the OSHA Laboratory Standard.
    • Reproductive Toxins – Reproductive toxins are substances that have adverse effects on various aspects of reproduction, including fertility, gestation, lactation, and general reproductive performance. When a pregnant woman is exposed to a chemical, the fetus may be exposed as well because the placenta is an extremely poor barrier to chemicals. Reproductive toxins can affect both men and women. Male reproductive toxins can in some cases lead to sterility.
    • Substances with a High Acute Toxicity – High acute toxicity includes any chemical that falls within any of the following OSHA-defined categories:
      • A chemical with a median lethal dose (LD50) of 50 mg or less per kg of body weight when administered orally to certain test populations.
      • A chemical with an LD50 of 200 mg less per kg of body weight when administered by continuous contact for 24 hours to certain test populations.
      • A chemical with a median lethal concentration (LC50) in air of 200 parts per million (ppm) by volume or less of gas or vapor, or 2 mg per liter or less of mist, fume, or dust, when administered to certain test populations by continuous inhalation for one hour, provided such concentration and/or condition are likely to be encountered by humans when the chemical is used in any reasonably foreseeable manner.

    Approval Procedure (top)

    Laboratory workers planning to use a particularly hazardous substance must first receive explicit written approval from their Principal Investigator and/or Chemical Hygiene Officer, per the Departmental Chemical Hygiene Plan. The following steps must be taken: 

    1.  Laboratory workers must complete a Particularly Hazardous Substance Use Approval form. Information required on the form includes:

    • Identity, physical characteristics, and health hazards of the substances involved
    • Consideration of exposure controls such as fume hoods, glove boxes and personal protective equipment
    • Designation of an area (hood, glove box, portion of lab, entire lab) specifically for experimental procedures with the substances involved
    • Plans for storage and secondary containment
    • Procedures for safe removal of contaminated waste
    • Decontamination procedures

    2. The laboratory worker submits the form to the Chemical Hygiene Officer and/or Principal Investigator and receives approval.

    3. The area where the PHS will be used is posted as a designated area. Signs for this purpose are available through EHS or may be made by the department or laboratory worker, as long as it includes the following information:

    for select carcinogens, reproductive toxins and high acute toxicity chemicals


    4.  The laboratory worker proceeds with the experiment, following the practices outlined in the Particularly Hazardous Substance Use Approval form, as well as the appropriate work practices included in the remainder of the Safe Work Practices and Procedures section of this manual. All work is conducted within the Designated Area.

    5.  The laboratory worker decontaminates all equipment and disposes of waste promptly, as outlined in the Particularly Hazardous Substance Use Approval form.

    Working Safely with Particularly Hazardous Substances (top)

    The increased hazard risk associated with Particularly Hazardous Substances (PHS) calls for more strict operating procedures in the laboratory:

    Work Habits

    • There should be no eating, drinking, smoking, chewing of gum or tobacco, application of cosmetics or storage of utensils, food or food containers in laboratory areas where PHS are used or stored.
    • All personnel should wash their hands and arms immediately after the completion of any procedure in which a PHS has been used and when they leave the laboratory.
    • Each procedure should be conducted with the minimum amount of the substance, consistent with the requirements of the work.
    • The laboratory worker should keep records of the amounts of each highly hazardous material used, the dates of use and the names of the users.
    • Work surfaces, including fume hoods, should be fitted with a removable liner of absorbent plastic-backed paper to help contain spilled materials and to simplify subsequent cleanup and disposal.

    Personal Protective Equipment

    • PHS may require more stringent use of personal protective equipment. Check the MSDS for information on proper gloves, lab clothing and respiratory protection.
    • Proper personal protective equipment must be worn at all times when handling PHS.
    • Lab clothing that protects street clothing, such as a fully fastened lab coat or a disposable jumpsuit, should be worn when PHS are being used. Laboratory clothing used while manipulating PHS should not be worn outside the laboratory area.
    • When methods for decontaminating clothing are unknown or not applicable, disposable protective clothing should be worn. Disposable gloves should be discarded after each use and immediately after overt contact with a PHS.


    • Most PHS work should be performed in a fume hood, glove box, or other form of ventilation. If the chemical may produce vapors, mists or fumes, or if the procedure may cause generation of aerosols, use of a fume hood is required.
    • A fume hood used for PHS must have an average face velocity of between 95 and 125 feet per minute. This measurement is noted on the hood survey sticker. If the hood has not been inspected within the past year, contact EHS at 8-5294 for re-inspection before using the hood.
    • A glove box should be used if protection from atmospheric moisture or oxygen is needed or when a fume hood may not provide adequate protection from exposure to the substance; e.g., a protection factor of 10,000 or more is needed.
    • Highly toxic gases must be used and stored in a vented gas cabinet connected to a laboratory exhaust system. Gas feed lines operating above atmospheric pressure must use coaxial tubing.

    Storage and Transportation

    • Stock quantities of PHS should be stored in a designated storage area or cabinet with limited access. Additional storage precautions (i.e., a refrigerator, a hood, a flammable liquid storage cabinet) may be required for certain compounds based upon other properties.
    • Containers must be clearly labeled.
    • Double containment should also be considered. Double containment means that the container will be placed inside another container that is capable of holding the contents in the event of a leak and provides a protective outer covering in the event of contamination of the primary container.
    • Containers should be stored on trays or pans made of polyethylene or other chemically resistant material.
    • Persons transporting PHS from one location to another should use double containment to protect against spills and breakage.

    Vacuum Lines and Services

    • Each vacuum service, including water aspirators, should be protected with an absorbent or liquid trap to prevent entry of any PHS into the system.
    • When using volatile PHS, a separate vacuum pump should be used. The procedure should be performed inside a fume hood.

    Decontamination and Disposal

    • Contaminated materials should either be decontaminated by procedures that decompose the PHS to produce a safe product or be removed for subsequent disposal.
    • All work surfaces must be decontaminated at the end of the procedure or work day, whichever is sooner.
    • Prior to the start of any laboratory activity involving a PHS, plans for the handling and ultimate disposal of contaminated wastes and surplus amounts of the PHS should be completed. EHS can assist in selecting the best methods available for disposal.

    Section 7K: Pyrophorics
    Section 7I: Laboratory Equipment

    Section 7K: Pyrophorics - Air and Water Reactives

    SECTION 7: Safe Work Practices and Procedures

    7K: Pyrophorics - Air and Water Reactives

    Certain stock reagents and in-situ products are pyrophoric, reacting violently when exposed to water and humid or dry air.  These chemicals are useful to research and many are essential to catalyze certain reactions or are incorporated into final products.  To handle these materials safely, review the Aldrich technical bulletins “Handling Air-Sensitive Reagents” and “Handling Pyrophoric Reagents”.  Some examples of pyrophoric materials include:

    Exposure to air or moisture can cause these materials to evolve heat, fire, flammable or corrosive byproducts by violent decomposition. Since they are typically packaged and stored under an inert atmosphere, under oil, or within a solvent, appropriate methods must be utilized to preserve the material during storage and while dispensing. See Section 7E Highly Toxic Gases for work with pyrophoric gases.

    Required Work Practices (top)

    Detailed information about transferring pyrophorics can be found in Aldrich technical bulletins “Handling Air-Sensitive Reagents” and “Handling Pyrophoric Reagents”.

    The following general guidelines must be followed while working with pyrophoric materials.

    • Know the properties and hazards of all chemicals you are using through adequate research and study, including reading the label and SDS.
    • Select and obtain all necessary materials to dispense and use the reagent(s) safely.
      • Dryboxes are used to supply an inert atmosphere to prevent pyrophoric reactions with air.
      • Fumehoods do not supply an inert atmosphere; however, they can be used for ventilation and staging the reaction apparatus.  The sash should be kept lowered to assist with containment in event of a violent reaction and to provide a barrier between the lab worker and the reaction.
      • Flex syringes (double-tipped needles) can be used for transferring materials.
        • Flex Syringes are constructed of tubing with needles attached to both ends for materials transfer through septa. A supply of low-pressure inert gas can be used to introduce the material to a reaction vessel, graduated addition funnel or graduated syringe. Tubing with a single needle may be needed to introduce the inert gas.


        • Appropriate glassware and reaction equipment
          • Ensure your glassware is DRY before assembly and introducing pyrophorics
          • Thoroughly purge all air from the apparatus with the proper inert gas
          • Use secure fittings, keep air-tight with a light coat of vacuum grease
          • Secure septa to all addition/withdrawal orifices
          • Incorporate bubblers filled with mineral oil to prevent air backflow
          • Use pressure rated glassware and fittings for pressurized reactions
        • Inert gas for purging air and material transfer
          • Nitrogen is not suitable for all materials, consult the MSDS
      • Syringes may also be used to withdraw small quantities of liquid reagent (<50 mL) from containers when a supply of inert gas is provided to displace the quantity withdrawn.
        • Ensure the syringe is completely DRY and purged with appropriate inert gas
        • Insert a line inot the septum, connected to a mineral oil-filled bubbler to prevent overpressure (not shown in picture below)
        • Insert a low-pressure inert gas source line into the septum
        • Insert an extraction syringe into the septum and slowly withdraw reagent

      • Select and use the appropriate personal protective equipment, see below.
      • Never work alone with pyrophorics.  Ensure someone can see or hear you.
      • Purchase quantities that will ensure use of the entire product within one year.
      • Use containers with transfer septa (i.e. Aldrich Sure/Seal) for liquid reagents.
        • septa prevent exposure to air and moisture and allow you to safely transfer the pyrophoric material when an inert working atmosphere is not available.
      • Visually check the container and reaction vessel septa for degradation before use.
      • A MetL-X fire extinguisher or powdered lime should be available in the lab.
        • ABC and CO2 extinguishers can cause some pyrophorics to react more vigorously.
        • Powdered lime can be used to cover spills and slow the reaction with air/humidity.
          • Lime is hydroscopic; keep storage containers closed to prevent absorption of atmospheric moisture.
      • Do not clean up spills.  Contain the spill and/or extinguish the fire only if you can do so safely. Evacuate the lab and contact Public Safety (911 from a campus or 609-258-7882 from a cell phone) immediately.

      Recommended Personal Protective Equipment (top)

      • Wear closed toed shoes made of a nonporous material, leather is preferred.
      • Use a face shield and chemical splash goggles to protect your face.
      • Wear a cloth labcoat or apron that can be quickly removed if needed.
        • Do not use plastic that can melt and adhere to your clothing/skin in event of a fire.
      • Use gloves made of a material resistant to the solvent/reagent.
      • Fire-resistant outer gloves with good dexterity are recommended.
      • Know where the nearest safety shower is from the reaction area.

      In The Event Of An Emergency (top)
      • If there is fire on your clothing or skin, stop-drop-and roll, unless you are within a few feet of a safety shower.
      • Keep in mind that unreacted materials may reignite until they are washed off.
      • If you are contaminated with a pyrophoric, remove your contaminated clothing while using the safety shower.  The copious amounts of water will flush away the heat of reaction.  If you have significant amounts of dry reactive compound on your body, you may brush off the bulk of it before you enter the shower, however only if it is not reacting.
      • Do not clean up spills.  Contain the spill and/or extinguish the fire only if you can do so safely. Evacuate the lab and contact Public Safety (911 from a campus or 609-258-3333 from a cell phone) immediately.
      • A MetL-X fire extinguisher or powdered lime should be available in the lab.
        • ABC and CO2 extinguishers can cause some pyrophorics to react more vigorously.
        • Powdered lime can be used to cover spills and slow the reaction with air/humidity.

      Additional Related Resources (top)

      Detailed information about transferring pyrophorics can be found in Aldrich technical bulletins “Handling Air-Sensitive Reagents” and “Handling Pyrophoric Reagents”.

      The following articles account a fatal incident involving a UCLA researcher working with t-butyllithium. "Deadly UCLA lab fire leaves haunting questions", "Researcher Dies After Lab Fire - UCLA research assistant burned in incident with tert-butyl lithium"

      A peer-reviewed publication "Safe handling of organolithium compounds in the laboratory" made available by the Division of Chemical Health and Safety of the American Chemical Society.

      Section 7L: Nanotechnology
      Section 7J: Particularly Hazardous Substances

    Section 7L: Nanotechnology

    SECTION 7: Safe Work Practices and Procedures


    Nanomotor (click to see in motion)


    Definition and Examples

    Nanotechnology is the field of science dealing with material specifically engineered to sizes of 100 nanometers (ηm – 10-9 m) or less. Nanoparticles are produced for their unique characteristics not attributed to common material dimensions. The different types of materials that are used in nanotechnology research and application varies widely; however, here are a few of the more common ones:

    Although many of these new hazards are still being investigated and toxicology research is in progress, few solid conclusions have been made about many nanomaterials. There are many things that we still do not know about this new technology. To properly protect against the unknown hazards that are involved while working with nanoparticles, conservative measures and best management practices must be exercised.

      • carbon
      • silver
      • gold
      • silica
      • titanium
      • polymers



    Potential Hazards (top)

    NIOSH (National Institute for Occupational Safety and Health) has determined the following potential exposure and health concerns:

    • The potential for nanomaterials to enter the body is among several factors that scientists examine in determining whether such materials may pose an occupational health hazard. Nanomaterials have the greatest potential to enter the body through the respiratory system if they are airborne and in the form of respirable-sized particles (nanoparticles). They may also come into contact with the skin or be ingested.
    • Based on results from human and animal studies, airborne nanoparticles can be inhaled and deposit in the respiratory tract; and based on animal studies, nanoparticles can enter the blood stream, and translocate to other organs.
    • Experimental studies in rats have shown that equivalent mass doses of insoluble incidental nanoparticles are more potent than large particles of similar composition in causing pulmonary inflammation and lung tumors. Results from in vitro cell culture studies with similar materials are generally supportive of the biological responses observed in animals.
    • Studies in workers exposed to aerosols of some manufactured or incidental microscopic (fine) and nanoscale (ultrafine) particles have reported adverse lung effects including lung function decrements and obstructive and fibrot­ic lung diseases. The implications of these studies to engineered nanoparticles, which may have different particle properties, are uncertain.


    Nanoparticle gold solutions

    Recommended Work Practices (top)

    • Conduct a thorough risk assessment  and take conservative measures to prevent exposure
    • Work with nanomaterials in liquid media whenever possible
    • Wear impervious gloves, labcoats or cleanroom suits, chemical splash goggles
    • Use enclosed control systems, such as a glovebox, for work with dry nanoparticles or when potential aerosol generation exists
    • HEPA filtration and wet wiping methods are both effective means of removing nanoparticle contamination

    Additional Related Resources (top)

    NIOSH - Approaches to Safe Nanotechnology
    Strategic Plan for NIOSH Nanotechnology Research and Guidance
    IRSST - Best Practices Guide to Synthetic Nanoparticle Risk Management

      Contact EHS for further guidance and recommendations to handle nanoparticle safely.

      Section 8: Chemical Spills
      Section 7K: Pyrophorics

      Section 8: Chemical Spills

      SECTION 8: Chemical Spills

      General information about cleaning up chemical spills is available in the Chemical Spill Procedures section of the EHS web page. This section contains information regarding:

      Pre-planning is essential. Before working with a chemical, the laboratory worker should know how to proceed with spill cleanup and should ensure that there are adequate spill control materials available. EHS also maintains general chemical spill kits for use by labs if no other control materials are immediately available.

      Preventing Spills (top)

      Most spills are preventable. The following are some tips that could help to prevent or minimize the magnitude of a spill:

      • Place chemical containers being used in a hood or lab bench area that reduces the possibility of accidentally knocking over a container.
      • Keep all unused reagents in thier appropriate storage area and keep your work area clean of needles equipment and clutter.
      • Plan your movements. Look where you are reaching to ensure you will not cause a spill.
      • Avoid transporting chemicals from the stockroom during periods of high traffic in the hallways such as between classes.
      • Transport chemical containers in a chemical carrier or cart.
      • Place absorbent plastic backed liners on benchtops or in fume hoods where spills can be anticipated. For volumes of liquid larger than what can be absorbed by liners, use trays.

      Followed the guidelines outlined for safe storage of chemicals.

      Section 9: Laboratory Waste Disposal
      Section 7L: Nanotechnology

      Section 9: Laboratory Waste Disposal

      Section 10: Chemical-Specific Issues

      SECTION 10: Chemical-Specific Issues

      Section 11: Anecdotes
      Section 9: Laboratory Waste Disposal

      Section 11: Anecdotes

      SECTION 11: Anecdotes

      Accidents do happen in Princeton University laboratories. The following are accounts of a few incidents that help to illustrate the need for the safety precautions outlined in this manual.

      Improper Shelving (top)

      Wall-Mounted Shelves Collapse

      There have been several incidents where wall-mounted shelves detached and fell onto desks and other work surfaces, dumping the shelving and books all over the work area. In one case, a person working nearby was injured as a result. In each instance, the shelves were heavily loaded and either exceeded the load capacity of the shelving or was incorrectly installed.

      Shelf of Chemical Storage Cabinet Collapses

      The bottom shelf of an organic chemical storage cabinet spontaneously collapsed. This shelf was not a moveable shelf, but a bottom panel contributing to the structural integrity of the cabinet. Fortunately, the drop was only a few inches and none of the bottles of chemicals were broken.

      The cabinet was constructed of thin plywood with particle board shelves attached to a pressed paperboard backing. This type of cabinet is not appropriate for chemical storage.

        • Wall-mounted shelving should have heavy-duty brackets and standards and should be attached to studs or solid blocking.
        • For books and periodicals, bookcases are preferable to wall-mounted shelving.
        • Only sturdy wood or metal cabinets should be used for chemical storage.
        • Be sure to check the shelf load capacity before using any storage cabinets or shelving units.
        • See Chemical Storage Guidelines for more information.

      Fires (top)

      Fire/Burn from Heating Flammable Solvent with Heat Gun

      A laboratory worker was using a heat gun to heat approximately 0.5 liters of heptane in a Pyrex beaker by hand over an open bench. A splash of heptane came in contact with the elements of the heat gun, igniting the heptane and causing him to toss the beaker away from him. The sleeve of the worker's shirt caught fire.  The flaming beaker landed on another work surface, spreading the fire to his computer. The worker immediately used a safety shower to put out the fire on his clothing, then used a dry chemical fire extinguisher to put out the other fire.

      The worker received burns to his hand. The computer containing his thesis was destroyed by the powder from the extinguisher.

      Hood Fire Involving Unattended Operation with Hexane Near Hot Plate

      A fire erupted inside a hood containing two reactions running unattended. A laboratory worker had placed nitrobenzene inside an oil bath atop a hot plate. The hot plate had been operating for three days, heating the oil bath to 200° C. A plastic squeeze bottle of hexane was placed next to the hot plate. Eventually, the squeeze bottle warmed enough to pressurize the container, forcing liquid hexane out of the bottle and onto the hot plate, where it ignited. Another laboratory noticed the smoke and attempted to put out the fire using a dry chemical extinguisher. A maintenance worker also noticed the fire and assisted the laboratory worker. Their attempts were not successful.

      The fire department was dispatched. Since the Emergency Information Poster on the door to the laboratory was inaccurate and there was a significant language barrier between the laboratory worker and the fire department personnel, a hazmat response team was dispatched. Frick, New Frick and Hoyt were evacuated for more than three hours. The laboratory worker and the maintenance worker were showered and scrubbed by the hazmat team and their clothing was confiscated (it was later washed and returned to them).  While this was probably an overreaction by the emergency response personnel, it illustrates the implications of not having an accurate, up-to-date emergency information poster.

        • Flammable liquids should be handled in a fume hood to prevent accumulation of vapors.
        • Heat guns and other equipment capable of igniting flammable vapors should not be used to heat flammable vapors.
        • Heating operations should not be carried out by hand. Instead, a lab stand and clamps should be used for this type of work.
        • Carbon dioxide extinguishers should be used around sensitive equipment.  Dry powder extinguishers can damage such equipment.
        • If clothing is on fire, smother the flame by rolling on the ground or use a safety shower to extinguish the fire, as was done in this incident.
        • See Safe Work Practices - Flammable Materials and Electrical Safety for more information.
        • Containers of volatile liquids placed near heat sources can become pressurized.
        • Materials not involved in an experiment should be removed, as possible, to avoid having them become involved in a fire or other incident.
        • Keeping the Emergency Information Poster up-to-date helps to ensure a proportionate response by emergency response personnel.
        • Evaluate the potential problems related to experiments left unattended for days at a time.
        • See Safe Work Practices - Flammable Materials and Electrical Safety for more information

      Chemical Burns (top)

      Hydrofluoric Acid Burn from Trifluoracetic Acid

      A laboratory worker picked up a container of trifluoroacetic acid with her ungloved hand to move it. She did not notice that there was a small amount of residue on the glass. Several hours later, she experienced pain in the palm of her hand and the inside aspect of her thumb. The result was a serious burn that required skin grafting.  She was not aware that this type of burn could result from handling trifluoracetic acid.

      Trifluoracetic acid can form hydrofluoric acid upon contact with moisture. Hydrofluoric acid can cause deep burns that may not be painful for hours.

      Chemical Splash While Carrying Chemicals Incorrectly

      A laboratory worker received burns to the face and chest while carrying chemicals from one area of the laboratory to another. The worker placed unsealed centrifuge tubes filled with phenol-chloroform into a Styrofoam centrifuge tube shipping container. The Styrofoam broke and the phenol-chloroform splashed onto the worker’s face and dripped down the chest. The worker immediately flushed the area with a drench hose, but still suffered from second-degree burns to the face, chest and abdomen. Fortunately, the worker was wearing chemical splash goggles and did not receive burns to the eyes.

      Overpressurization of Gel Column Causes Chemical Splash

      A laboratory worker was pouring chloroform though a gel column inside a fume hood. Due to incorrect equipment configuration, pressure built up in the column and caused the glassware at the top of the column to break, spraying chloroform out of the hood, onto the worker’s face, eyes and clothing.

      The laboratory worker was wearing safety glasses, rather than chemical splash goggles. The chloroform seeped through the opening at the top of the glasses and burned both eyes. The lens of the safety glasses were partially dissolved by the chloroform. The worker did use a safety shower immediately, but was too embarrassed to remove his sweater in the presence of other laboratory workers. As a result, he suffered from second degree burns on both arms where the chloroform soaked through the sweater.

      The set-up of the apparatus was changed to allow the hood of the sash to be lowered when the chloroform is being poured, providing an additional shield between the worker and the chemical and lowering the potential spray below eye level.

      Failure to Remove Contaminated Clothing Exacerbates Chemical Burns

      There have been several incidents, usually involving phenol, where laboratory workers spilled a chemical on his or her pants. In all cases, the worker bypassed the safety shower and entered a restroom to remove the pants and rinse the leg. In each case, the worker put the contaminated pants back on and either went home to rinse further or went to University Health Services at McCosh. All resulted in second degree burns that could have been minimized by taking off the contaminated clothing and rinsing immediately using a safety shower or drench hose.

      Mixing Incompatible Wastes

      A laboratory worker was cleaning out chemicals from an old refrigerator. Wearing gloves, chemical splash goggles and a lab coat (over shorts), the worker was segregating the chemicals into several different waste containers. He found a small bottle of iodine monochloride, and not knowing the physical properties of the chemical, began to pour it into a jar with other liquid wastes.   The waste container suddenly began fuming vigorously, startling the worker and causing the worker to drop the bottle of iodine monochloride.  Several drops of the chemical splashed onto the worker's leg, causing a second degree burn.

      The iodine monochloride reacted with a chemical in the waste container. The worker was fortunate that the reaction did not produce significant amounts of hazardous vapors. Had the worker been wearing long pants, the burn might have been avoided.

        • Know the hazards of the chemicals involved before handling them.
        • Always assume containers are contaminated and wear appropriate gloves when handling chemical containers.
        • Keep a hydrofluoric acid burn kit in the laboratory when working with hydrofluoric acid or trifluoracetic acid.
        • Appropriate eye and face protection helped to minimize the chemical burn.
        • Wear a closed lab coat when working with hazardous materials.
        • Use a plastic centrifuge rack instead of a Styrofoam packing container, particularly when transporting chemicals.
        • Keep hazardous materials that have the potential for splash below eye level.
        • Use care when working with pressure or vacuum to avoid pressurizing containers.
        • Wear a closed lab coat, chemical splash goggles and, if necessary, a face shield when there is a possibility of a significant chemical splash.
        • Remove contaminated clothing while rinsing.
        • Keep the hood sash lowered and/or use shielding when working with pressurized containers.
        • Remove contaminated clothing while rinsing.
        • Wear appropriate personal protective equipment, including a closed lab coat when working with hazardous materials.
        • Do not put contaminated clothing back on.
        • Wash clothing separately or discard.  Many chemicals can permeate leather.  Discard any contaminated leather items.
        • Never mix chemicals unless you are certain of the consequences and are prepared to control the hazard.
        • Do not mix incompatible waste chemicals together.
        • Know the hazards of each chemical before working with it.
        • Wear pants and a closed lab coat when working with hazardous materials.
        • See Laboratory Waste Disposal for more information.

      Glass Vessel Ruptures (top)

      Glass Flask Rupture During Ozonolysis

      During an early attempt to scale up a procedure, a laboratory worker introduced ozone gas into a flask containing a small amount of organic material. The flask was set in a fume hood in a cooling bath designed to lower the experiment temperature to -85° C, 15° C below that which is normally used for such experiments. The sash of the fume hood was completely raised. During the procedure, the worker noticed that a deep blue color had developed in the flask, an indication that the concentration of ozone was increased. He attributed it to poor mixing and had started to increase the stir rate when the flask exploded. Flying glass embedded into his face, neck and safety glasses.

      The worker did not experience any injuries to his eyes. Many of the cuts on his face and neck required stitches. Shards of glass remain in the safety glasses even today.  

      Glass Flask Ruptures, Possibly Overpressurization by Liquid Nitrogen

      A 250 ml glass flask became overpressurized and burst, spraying two laboratory workers with shards of glass.

      Approximately 10 grams of styrene and a minute quantity of a drying agent were immersed in liquid nitrogen to keep the contents frozen. The laboratory worker then attached the flask to a vacuum pump to evacuate the flask, without success. Thinking the flask might have developed a crack, the laboratory worker removed the flask from the vacuum line and was defrosting it under warm water in the sink, holding it and examining it, when the flask ruptured.

      The best guess as to the cause of the rupture is that a small leak, perhaps a pinhole in the flask, developed while it was being frozen and that some liquid nitrogen entered the flask. When the flask was warmed, the liquid nitrogen vaporized (expansion ratio 696:1), overpressurizing the flask and leading to the explosion.

      The laboratory worker holding the flask suffered from several lacerations to the face, hands, chest and abdomen. The other worker, who was standing across the room, received lacerations to the abdomen. The worker holding the flask noted shards of glass embedded in his prescription safety glasses.

      The procedure was re-written such that under the same conditions, the stopcock will be unscrewed and the flask set in a catchbucket in the hood to allow the contents to warm up and vaporize, if volatile.

      Glass Waste Bottle Ruptures, Possible Reaction of Incompatible Chemical Wastes

      A graduate student sitting at a lab computer was surprised by a chemical waste bottle which burst and sprayed nitric acid and shards of glass all over the lab.

      Approximately 2L of nitric acid waste had been accumulated in a chemical waste bottle which originally contained methanol.  Over the course of 12-16 hours, it is likely that some residual methanol reacted with the nitric acid waste and created enough carbon dioxide to overpressurize the container.  Two other waste containers in the hood were severely damaged and several others were cracked or leaking.

      Fortunately, the laboratory worker was not injured.

        • The sash of the hood might have provided enough of a barrier to avoid injury. However, most sashes are not designed to protect against explosions.
        • Shielding should be used around any experiments that might explode.
        • A face shield would have protected the worker from the cuts on his face and neck.
        • Carefully evaluate the hazards before proceeding with a scaled-up experiment.
        • Appropriate eye protection helped to avoid a potentially serious eye injury.
        • Consider shielding operations involving vacuum or pressurization.
        • Be aware of the potential for pressurization when working with liquid nitrogen.
        • See Safe Work Practices - Pressure and Vacuum Systems for more information.
        • Chemical containers should be triple rinsed and dry before being used for waste accumulation.
        • Safety glasses should always be worn while in the laboratory, even while performing non-laboratory work.

      Incidents Involving Reactive Materials (top)

      Peroxide Detonation

      A laboratory worker attempted to use some anhydrous ethyl ether in a rotary evaporator extraction. The four-liter container of ether was nearly empty. While pouring the ether into the apparatus (inside a fume hood), he noticed that the liquid was oily and had a strange odor, so he decided not to use it. He poured the ether back into the can and went home.

      The next morning, he noticed a white residue inside the rotary evaporator. He used a metal spatula to scrape the residue from a glass joint, causing a detonation that shattered the glassware. The flying glass caused severe lacerations to the worker’s hands, face, ear and scalp. Fortunately, he was wearing safety glasses that protected his eyes from injury. Shards of glass were embedded in the lenses of the safety glasses. The sash of the hood was cracked and the light fixture inside the hood shattered.

      The can of ethyl ether was purchased 30 months before the incident and was likely opened about six months later. The container label clearly warned about the formation of peroxide in storage, despite the presence of a stabilizer.

      Lithium Aluminum Hydride Fire

      A laboratory worker was attempting to distill tetrahydrofuran (THF) using lithium aluminum hydride (LAH). THF is a highly flammable liquid that can cause severe eye irritation and central nervous system depression. LAH is a water-reactive, flammable solid.

      The laboratory worker was slowly pouring approximately 1 gram of LAH from a plastic bag into a flask containing 500 ml of THF inside a fume hood. A small amount of LAH leaked from a small hole in the bag, onto the surface of the hood and burst into flames, startling the worker and causing him to drop the remainder of the bag (8-10 grams of LAH) onto the fire. Concerned about the flask and bottle of THF inside the hood, the worker immediately removed his lab coat and placed it onto the fire in an attempt to smother it.

      Since the appropriate extinguishing agent was not available, .the worker pulled the flaming lab coat and LAH out of the hood onto the floor. Once the LAH fire had burned itself out, the worker used a dry chemical extinguisher to put out the coat fire.

      Since the incident, Met-L-X extinguishers were mounted inside the door of the laboratory. The laboratory worker keeps a supply of sand (in a plastic milk jug with the top cut off) on the floor at the side of the hood where this work is done.

      Potassium Metal Released from Pressurized Container

      A laboratory worker received burns to one hand when small pieces of potassium metal shot out of an alkali jet apparatus when the laboratory worker opened it for cleaning. The accident occurred because the worker accidentally opened the apparatus while the system was still under pressure. The burn was exacerbated by the fact that the worker rinsed the hand with a small amount of mineral oil rather than with copious amounts of water.

      To avoid a future occurrence, the worker installed a venting valve with a filter to allow venting prior to opening the device. In addition, plexiglas shielding is placed around the apparatus and the workers wear gloves, safety glasses and a face shield when opening the device.

        • Using appropriate personal protective equipment helped to avoid a potentially serious eye injury.
        • Discard peroxide forming chemicals six months after opening or one year after purchase. Unless you plan to use the entire contents within this time period, large containers such as the one involved in this incident should not be ordered.
        • Most hood sashes are not explosion-proof.  Consider the need for shielding of reactions that may result in exploding materials.
        • Do not use metal spatulas with peroxide forming compounds, since contamination with metals can lead to explosive decomposition. Ceramic, Teflon or wooden spatulas are recommended.
        • See Safe Work Practices - Peroxide Forming Compounds and Reactives for more information
        • Know the hazards of the materials, including appropriate extinguishing agents, before using chemicals.
        • Carbon dioxide reacts with LAH explosively; thus, a carbon dioxide extinguisher could have made the situation worse. A Met-L-X fire extinguisher (for flammable solids) or dry sand should have been immediately available.
        • Do not pour solids such as LAH directly from the container into another chemical or reaction vessel.  Measure out what is needed, then pour it.
        • The proper first aid for skin contact with potassium is to brush away visible metals and flush with copious amounts of water for at least 15 minutes.
        • Ensure reaction vessels are at atmospheric pressure before opening them.
        • Wear gloves, safety glasses and a face shield when working with pressurized equipment and hazardous materials.

      Electrical Shock (top)

      Electrical Shock from Laser Power Supply

      A laboratory worker noticed condensation on the high voltage power supply for a high powered laser. With the power still on, he wiped the moisture with a tissue, making contact with the exposed anode terminal at approximately 17,000 volts DC to ground.

      He received a severe electrical shock and second degree burns to his right thumb and abdomen. Witnesses stated that they heard a loud "snap" and then heard the laboratory worker scream and stagger out to the hallway. He was immediately met by a secretary, and told her "I got a shock" as he collapsed into her arms and onto the floor. He had no pulse and was not breathing. Public Safety officers were nearby and immediately started CPR. The ambulance crew arrived and was able to restore his heartbeat using a defibrillator.

      Fortunately, the laboratory worker lived to tell his story. He said that he knew that the power was on but was not aware that contact was possible at the high voltage terminals. The interlocks had been defeated and guards removed with no alternate guarding or precautions taken.

      Electrical Shock from Electrophoresis Unit

      A laboratory worker received a potentially fatal electrical shock when he accidentally touched a high voltage electrical connector on an electrophoresis device. The contact points were on the right elbow and right knee. Had one of the contacts been on the opposite side of the body, the shock could have been fatal.

      The primary cause of this incident was the existence of an exposed high voltage conductor in the form of a stackable banana plug at the device. When connected to the male plug on the device, the male connector plug was left exposed with no insulation or guarding.

        • Understand the operating characteristics of equipment before use.
        • Do not defeat machine safety interlocks.
        • Do not work around energized exposed conductors.
        • See Safe Work Practices - Electrical Safety for more information.
        • For information about laser safety, see the Laser Safety Training Guide.
        • The accident could have been avoided by eliminating all exposed conductors in connector cords and electrophoresis devices by either
          • fitting each electrophoresis with its own set of permanently attached connector cords to eliminate jacks and plugs entirely at this point; or
          • eliminating cords with stackable plugs on both ends by replacing the stackable plugs on one end with a female only jack (all electrophoresis devices should be fitted with male only plugs).
        • For more information, see Electrical Safety and Laboratory Equipment.

      Section 12: Ergonomics
      Section 10: Chemical-Specific Issues

      Section 12: Ergonomics

      SECTION 12: Ergonomics

      Ergonomics is the science of designing work areas or equipment for safe, comfortable and effective human use. Certain laboratory related tasks may place lab workers at an increased risk for developing repetitive strain injuries (RSI). Repetitive activities may cause discomfort and, if not properly modified, may lead to pain or reduced dexterity.

      Not everyone performing the same job tasks will develop a RSI. Listed below are the most common factors that may increase the risk for a RSI:

      • Awkward Body Postures: Any posture that places a body part out of a neutral position (i.e. twisting, poor posture, bending, over-reaching) may put increased strain on muscles, tendons, ligaments and joints.
      • Exertion: Maintaining a specific body position or exertion for long periods of time may result in pressure or force being placed on the soft tissues.
      • Repetition: Higher numbers of similar body movements over extended time periods may increase the risk of developing a RSI.
      • Contact Pressure: Pressure resulting from leaning against or resting a body part on a sharp edge or hard surface can constrict blood flow.

      Laboratory procedures may be repetitive or involve a variety of these risk factors.

      Pipetting (top)

      Certain laboratory procedures require frequent pipetting for extended periods of time, resulting in repetitive force on the thumbs, hands, forearm, or fingers. Stresses may be reduced by varying pipetting with other lab tasks that use different motions and muscle groups or by taking frequent, small rest breaks. Place receptacles for used pipette tips close to the work area to avoid frequent reaching. If it is an option, replace manually operated pipettes with electronic ones for larger workloads.

      Biological Safety Cabinets/Fume Hoods (top)

      Working in Biological Safety Cabinets (BSCs) or chemical fume hoods may require lab workers to bend forward frequently or assume awkward body postures. Users should take short breaks to alter their body posture, or to reduce contact pressure caused by leaning on sharp edges or hard surfaces. Keeping the viewing window of hood clean, and line of sight unobstructed, reduces eye strain and the need to assume awkward body positions.

      Microscopy (top)

      Operating a microscope for long hours may put increased strain on the neck, shoulders, eyes, lower back, arms and wrists. If sitting, use an adjustable chair that provides support to the back and legs. Ensure that your feet are flat on the floor or supported by a footrest. Avoid raising your shoulders and bending your neck for long periods of time while looking through the microscope’s eyepiece. Position the microscope as close as possible to reduce the need to bend forward. Take adequate small breaks, or vary microscopy with other job tasks.

      Computer Workstations (top)

      The following guidelines are intended to help workers understand and reduce health risks associated with computer workstations:

      • The keyboard and mouse should be directly in front of the operator at a height that favors a neutral posture. The objective is a posture with upper arms relaxed and wrists straight in line with the forearm.
      • The monitor should be positioned at a distance of approximately arm’s length and directly in front of the operator. The top of the screen should be no higher than eye level.
      • A well designed chair will favorably affect posture, circulation, the amount of effort required to maintain good posture, and the amount of strain on the back. An adjustable seat back is best for support of the lumbar region. The user should be able to adjust seat height and seat pan angle from a seated position.
      • Additional accessories may improve operator comfort. Document holders may minimize eye, neck and shoulder strain by positioning the document close to the monitor. A footrest should be used where the feet cannot be placed firmly on the floor. Task lamps should be used to illuminate source documents when room lighting is reduced.

      Appendix A: List of Particularly Hazardous Substances
      Section 11: Anecdotes

      Appendix A: Particularly Hazardous Substances

      Appendix A: Particularly Hazardous Substances

      NOTE: This list is not exhaustive. Please refer to the material safety data sheet to determine whether a chemical is a carcinogen, reproductive toxin or chemical with high acute toxicity.

      A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


      Chemical Name
      CAS Number
      A-alpha-C (2-Amino-9H-pyrido{2,3-b]indole)
      Carcinogen, Reproductive Toxin
      High acute toxicity
      Actinomycin D
      Adriamycin (Doxorubicin hydrochloride)
      AF-2; [2-(2-furyl)-3-(5-nitro-2-furyl)]acrylamide
      Carcinogen, Reproductive Toxin
      Allyl chloride
      Aluminum chloride
      Reproductive Toxin
      4-Aminobiphenyl (4-aminodiphenyl)
      3-Amino-9-ethylcarbazole hydrochloride
      High acute toxicity
      Anesthetic gases
      Reproductive Toxin
      ortho-Anisidine hydrochloride
      Antimony oxide (Antimony trioxide)
      Arsenic (inorganic arsenic compounds)
      Reproductive Toxin
      Arsenic pentafluoride gas
      High Acute Toxicity
      Arsine gas
      High Acute Toxicity


      Carcinogen, Reproductive Toxin
      Benzidine [and its salts]
      Benzo [b] fluoranthene
      Benzo [j] fluoranthene
      Benzo [k] fluoranthene
      Benzo [a] pyrene
      Carcinogen, Reproductive Toxin
      Benzyl chloride
      Carcinogen, High Acute Toxicity
      Benzyl violet 4B
      Beryllium and beryllium compounds
      Betel quid with tobacco
      N,N,-Bis(2-chloroethyl)-2-naphthylamine (Chlornapazine)
      Bischloroethyl nitrosourea (BCNU) (Carmustine)
      Bis (chloromethyl) ether
      Bitumens, extracts of steam-refined and air-refined
      Boron trifluoride
      High Acute Toxicity
      Bracken fern
      High Acute Toxicity
      1,4-Butanediol dimethanesulfonate (Busulfan)
      Butylated hydroxyanisole


      Cadmium and cadmium compounds
      Carcinogen, Reproductive Toxin
      Carbon disulfide
      Reproductive Toxin
      Carbon tetrachloride
      Carcinogen, Reproductive Toxin
      Carbon-black extracts
      Reproductive Toxin
      Ceramic fibers
      Chlordecone (Kepone)
      Chlorendic acid
      Chlorinated paraffins
      Chlorine gas
      High Acute Toxicity
      Chorine dioxide
      High Acute Toxicity
      Chlorine trifluoride
      High Acute Toxicity
      Chloroethane (Ethyl chloride)
      1-(2-Chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea (Methyl-CCNU)
      Reproductive Toxin
      Chloromethyl methyl ether
      Reproductive Toxin
      Chromium (hexavalent)
      Chromium trioxide
      Carcinogen, Reproductive Toxin
      C. I. Acid Red 114
      C. I. Basic Red 9 monohydrochloride
      Ciclosporin (Cyclosporin A; Cyclosporine)
      Cinnamyl anthranilate
      Citrus Red No. 2
      Cobalt metal powder
      Cobalt [II] oxide
      Conjugated estrogens
      Cyanogen chloride
      High Acute Toxicity
      Cyclophosphamide (anhydrous)
      Cyclophosphamide (hydrated)


      D&C Orange No. 17
      D&C Red No. 8
      D&C Red No. 9
      D&C Red No. 19
      Dantron (Chrysazin; 1,8-Dihydroxyanthraquinone)
      DDD (Dichlorodiphenyldichloroethane)
      DDE (Dichlorodiphenyldichloroethylene)
      DDT (Dichlorodiphenyltrichloroethane)
      DDVP (Dichlorvos)
      High Acute Toxicity
      2,4-Diaminoanisole sulfate
      4,4’-Diaminodiphenyl ether (4,4’-Oxydianiline)
      Diaminotoluene (mixed)
      Diazomethane gas
      High Acute Toxicity
      Diborane gas
      High Acute Toxicity
      1,2-Dibromo-3-chloropropane (DBCP)
      Carcinogen, Reproductive Toxin
      3,3’-Dichloro-4,4’-diaminodiphenyl ether
      Diesel engine exhaust
      Diethyl sulfate
      Diglycidyl resorcinol ether (DGRE)
      3,3’-Dimethoxybenzidine (ortho-Dianisidine)
      3,3’-Dimethoxybenzidine dihydrochloride(ortho-Dianisidine dihydrochloride)
      Dimethylcarbamoyl chloride
      Dimethyl formamide
      Reproductive Toxin
      1,1-Dimethylhydrazine (UDMH)
      Dimethyl mercury
      High Acute Toxicity
      Dimethyl sulfate
      Carcinogen, High Acute Toxicity
      Dimethyl sulfide
      High Acute Toxicity
      Dinitrooctyl phenol
      Reproductive Toxin
      Diphenylhydantoin (Phenytoin)
      Diphenylhydantoin (Phenytoin), sodium salt
      Direct Black 38 (technical grade)
      Direct Blue 6 (technical grade)
      Direct Brown 95 (technical grade)
      Reproductive Toxin
      Disperse Blue 1
      Reproductive Toxin


      Carcinogen, Reproductive Toxin
      Estradiol 17ß
      2-Ethoxy ethanol
      Reproductive Toxin
      2-Ethoxyethyl acetate
      Reproductive Toxin
      Ethyl acrylate
      Ethyl methanesulfonate
      Ethylene chlorohydrin
      High Acute Toxicity
      Ethylene dibromide
      Carcinogen, Reproductive Toxin
      Ethylene dichloride (1,2-Dichloroethane)
      Ethylene fluorohydrin
      High Acute Toxicity
      Ethylene glycol monoethyl ether
      Reproductive Toxin
      Ethylene glycol monomethyl ether
      Reproductive Toxin
      Ethylene oxide
      Carcinogen, Reproductive Toxin
      Ethylene thiourea
      Carcinogen, Reproductive Toxin
      Reproductive Toxin


      Fluorine gas
      High Acute Toxicity
      High Acute Toxicity
      Carcinogen, Reproductive Toxin


      Glu-P-1 (2-Amino-6-methyldipyrido[1,2-a:3’,2’- d]imidazole)
      Glycol ethers
      Reproductive Toxin
      Gyromitrin (Acetaldehyde methylformylhydrazone)


      Reproductive Toxin
      HC Blue 1
      Heptachlor epoxide
      Hexachlorocyclohexane (technical grade)
      Reproductive Toxin
      Hexamethylene diiosocyanate
      High Acute Toxicity
      Carcinogen, Reproductive Toxin
      Reproductive Toxin
      Carcinogen, Reproductive Toxin
      Hydrazine sulfate
      Hydrazobenzene (1,2-Diphenylhydrazine)
      Hydrogen Cyanide
      High Acute Toxicity
      Hydrogen Fluoride
      High Acute Toxicity


      Indeno [1,2,3-cd]pyrene
      Iodine (inhalation only)
      High Acute Toxicity
      IQ (2-Amino-3-methylimidazp[4,5-f]quinoline)
      Iron dextran complex
      Iron pentacarbonyl
      High Acute Toxicity
      Isopropyl formate
      High Acute Toxicity


      Reproductive Toxin


      Lead (inorganic compounds)
      Reproductive Toxin
      Lead acetate
      Lead phosphate
      Lead subacetate


      Me-A-alpha-C (2-Amino-3-methyl-9H-pyrido[2,3-b]indole)
      Medroxyprogesterone acetate
      Methacryloyl chloride
      High Acute Toxicity
      Reproductive Toxin
      2-Methoxyethyl acetate
      Reproductive Toxin
      8-Methoxypsoralen with ultraviolet A therapy
      5-Methoxypsoralen with ultraviolet A therapy
      Methyl acrylonitrile
      High Acute Toxicity
      2-Methylaziridine (Propyleneimine)
      Methylazoxymethanol acetate
      Methyl cellosolve
      Reproductive Toxin
      Methyl chloride
      Reproductive Toxin
      Methyl chloroformate
      High Acute Toxicity
      4,4’-Methylene bis(2-chloroaniline)
      4,4’-Methylene bis(N,N-dimethyl)benzenamine
      4,4’-Methylene bis(2-methylaniline)
      Methylene biphenyl isocyanate
      High Acute Toxicity
      4,4’-Methylenedianiline dihydrochloride
      Methyl fluoroacetate
      High Acute Toxicity
      Methyl fluorosulfate
      High Acute Toxicity
      Methylhydrazine and its salts
      Carcinogen, High Acute Toxicity
      Methyl mercury and other organic forms
      High Acute Toxicity
      Methyl methanesulfonate
      Reproductive Toxin
      Methyl trichlorosilane
      High Acute Toxicity
      Methyl vinyl ketone
      High Acute Toxicity
      Michler’s ketone
      Mitomycin C
      5-(Morpholinomethyl)-3-[(5-nitro-furfurylidene)-amino]-2 oxalolidinone
      Mustard Gas


      Nickel and certain nickel compounds
      Nickel carbonyl
      Carcinogen, High Acute Toxicity
      Nickel subsulfide
      Nitrilotriacetric acid
      Nitrilotriacetric acid, trisodium salt monohydrate
      Nitrofen (technical grade)
      Nitrogen dioxide
      High Acute Toxicity
      Nitrogen mustard (Mechlorethamine)
      Nitrogen mustard hydrochloride (Mechlorethamine hydrochloride)
      Nitrogen mustard N-oxide
      Nitrogen mustard N-oxide hydrochloride
      Nitrogen tetroxide
      High Acute Toxicity
      Nitrogen trioxide
      High Acute Toxicity
      Nitrous Oxide
      Norethisterone (Norethindrone)


      Ochratoxin A
      Osmium tetroxide
      High Acute Toxicity
      Oxygen difluoride gas
      High Acute Toxicity
      High Acute Toxicity


      Panfuran S
      Phenazopyridine hydrochloride
      Phenoxybenzamine hydrochloride
      Phenyl glycidyl ether
      Phenylhydrazine and its salts
      o-Phenylphenate, sodium
      High Acute Toxicity
      Phosphine gas
      High Acute Toxicity
      Phosphorus oxychloride
      High Acute Toxicity
      Phosphorus pentafluoride gas
      High Acute Toxicity
      Phosphorus trichloride
      High Acute Toxicity
      Polybrominated biphenyls
      Polychlorinated biphenyls
      Ponceau MX
      Ponceau 3R
      Potassium bromate
      Procarbazine hydrochloride
      1,3-Propane sultone
      Propylene glycol monomethyl ether
      Reproductive Toxin
      Propylene oxide


      Reproductive Toxin


      Saccharin, sodium
      Selenium sulfide
      Silica, crystalline
      Sodium azide
      High Acute Toxicity
      Sodium cyanide (and other cyanide salts)
      High Acute Toxicity
      Styrene oxide
      Reproductive Toxin


      Talc´ containing asbestiform fibers
      Testosterone and its esters
      2,3,7,8-Tetrachlorodibenzo-para-dioxin (TCDD)
      Tetrachloroethylene (Perchloroethylene)
      p-a, a, a-Tetrachlorotoluene
      4,4´ - Thiodianiline
      Thorium dioxide
      TOK (herbicide)
      Reproductive Toxin
      Toluene diisocyanate
      ortho-Toluidine hydrochloride
      Toxaphene (Polychorinated camphenes)
      Trichlormethine (Trimustine hydrochloride)
      Trimethyltin chloride
      High Acute Toxicity
      Triphenyltin hydroxide
      Tris (aziridinyl)-para-benzoquinone (Triaziquone)
      Tris (1-aziridinyl) phosphine sulfide (Thiotepa)
      Tris (2-chloroethyl) phosphate
      Tris (2,3-dibromopropyl) phosphate
      Trp-P-1 (Tryptophan-P-1)
      Trp-P-2 (Tryptophan-P-2)
      Trypan blue (commercial grade)


      Uracil mustard
      Urethane (Ethyl carbamate)


      Vinyl bromide
      Vinyl chloride
      Carcinogen, Reproductive Toxin
      4-Vinyl-1-cyclohexene diepoxide (Vinyl cyclohexene dioxide)
      Vinyl trichloride (1,1,2-Trichloroethane)



      2,6-Xylidine (2,6-Dimethylaniline)




      Appendix B: Reproductive Toxins

      Section 12: Ergonomics
      Section 7J: Particularly Hazardous Substances Safe Work Practices/Procedures

      Appendix B: Reproductive Toxins

      Appendix B: Reproductive Toxins

      PLEASE NOTE: This list is not exhaustive. Please check the safety data sheet (SDS) to determine if the chemical is considered a reproductive toxin.

      Chemical Name 
      CAS Number
      Anesthetic gases
      Aluminum chloride
      Carbon disulfide
      Carbon tetrachloride
      Chromium trioxide
      Dimethyl formamide
      Ninitrooctyl phenol
      DBCP (1,2-dibromo-3-chloropropane)
      2-Ethoxy ethanol
      2-Ethoxyethyl acetate
      Ethylene dibromide
      Ethylene glycol monoethyl ether
      Ethylene glycol monomethyl ether
      Ethylene oxide
      Ethylene thiourea
      Glycol ethers
      Lead (inorganic compounds)
      2-Methoxyethyl acetate
      Methyl cellosolve
      Methyl chloride
      Propylene glycol monomethyl ether
      Propylene glycol monomethyl ether acetate
      Propylene oxide
      Vinyl chloride

      Appendix C: Materials with High Acute Toxicity
      Appendix A: Particularly Hazardous Substance List

      Appendix C: Materials With High Acute Toxicity

      Appendix C: Materials with High Acute Toxicity

      NOTE: This list is not exhaustive. Please refer to the material safety data sheet to determine if other chemicals meet the specifications as high acute toxicity.


      A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


      CAS Number



      Arsenic pentafluoride gas
      Arsine gas


      Benzyl chloride
      Boron trifluoride


      Chlorine gas
      Chorine dioxide
      Chlorine trifluoride
      Cyanogen chloride


      Diazomethane gas
      Diborane gas
      Dimethyl mercury
      Dimethyl sulfate
      Dimethyl sulfide


      Ethylene chlorohydrin
      Ethylene fluorohydrin


      Fluorine gas


      Hexamethylene diiosocyanate
      Hydrogen cyanide
      Hydrogen flouride


      Iron pentacarbonyl
      Isopropyl formate


      Methacryloyl chloride
      Methyl acrylonitrile
      Methyl chloroformate
      Methylene biphenyl isocyanate
      Methyl fluoroacetate
      Methyl fluorosulfate
      Methyl hydrazine
      Methyl mercury and other organic forms
      Methyl trichlorosilane
      Methyl vinyl ketone


      Nickel carbonyl
      Nitrogen dioxide
      Nitrogen tetroxide
      Nitrogen trioxide


      Osmium tetroxide
      Oxygen difluoride gas


      Perchloromethlyl mercaptan
      Phosgene gas
      Phosphine gas
      Phosphorus oxychloride
      Phosphorus pentafluoride gas
      Phosphorus trichloride


      Selenium hexafluoride gas
      Silicon tetrafluoride gas
      Sodium azide
      Sodium cyanide (and other cyanide salts)
      Stibine gas
      Sulfur monochloride
      Sulfur pentafluoride
      Sulfur tetrafluoride gas
      Sulfuryl chloride


      Tellurium hexafluoride
      Tetramethyl succinonitrile
      Thionyl chloride
      Trimethyltin chloride


      Appendix B: Reproductive Toxins
      Appendix D: Health and Safety Design Considerations for Laboratories

      Appendix D: Health & Safety Design Considerations for Laboratories

      Appendix D: Health & Safety Design Considerations for Laboratories

      For any new construction or renovation of laboratory areas, consider health, safety and regulatory compliance issues early in the design stage of the project. The following outlines some of these issues:

      Layout (top)

      • Laboratory space should be physically separate from personal desk space, meeting space and eating areas. Workers should not have to go through a laboratory space where hazardous materials are used in order to exit from non-laboratory areas. Consider making visible separation between lab and non-lab space, for instance with different flooring.
      • Fire-rated hallway doors should have magnetic hold-open features, such that the door will close in the event of an alarm.
      • Doors to laboratories should not be fire-rated unless necessary.
      • Entryways should have provisions for mounting emergency information posters and other warning signage immediately outside the laboratory (e.g., on the door).
      • Each door from a hallway into a lab should have a view panel to prevent accidents from opening the door into a person on the other side and to allow individuals to see into the laboratory in case of an accident or injury.
      • Laboratory areas with autoclaves should have adequate room to allow access to the autoclave and clearance behind it for maintenance. There should also be adequate room for temporary storage of materials before and after processing. Autoclave drainage should be designed to prevent or minimize flooding and damage to the floor.
      • For laboratories using radioactive materials:
      • Eating and drinking areas should be physically separate and conveniently located.
      • Allow for security of laboratory and materials.
      • Consider designing the lab to allow separation of radioactive materials use from other laboratory activities.

      Furniture and Fixtures (top)

      • Work surfaces should be chemical resistant, smooth, and readily cleanable, such as chemical-grade Formica.
      • Work surfaces, including computer areas, should incorporate ergonomic features, such as adjustability, appropriate lighting and equipment layout.
      • Benchwork areas should have knee space to allow room for chairs near fixed instruments, equipment or for procedures requiring prolonged operation.
      • Handwashing sinks for particularly hazardous chemicals or biological agents may need elbow or electronic controls.
      • Wet chemical laboratories and darkrooms should have solvent resistant coved flooring using sheet goods rather than tile, particularly in areas where fume hoods are located.
      • Do not install more sinks or cupsinks than are necessary. Unused sinks may develop dry traps, resulting in odor complaints.
      • Sink faucets and hose bibs that are intended for use with attached hoses are provided with back siphon prevention devices.

      Storage (top)

      • Cabinets for chemical storage should be of solid, sturdy construction. Hardwood or metal shelving is preferred. Some may require ventilation.
      • Materials of construction should be carefully considered where corrosive materials will be stored, e.g., corrosive-resistant liners or trays on shelves, location away from copper fittings, etc.
      • Allow space within the building for any central chemical and biological or radioactive waste storage needs.
      • Wall shelving should have heavy-duty brackets and standards and should be attached to studs or solid blocking. For office spaces, bookcases are preferable to wall-mounted shelving.
      • Flammable liquid storage needs should be defined in advance so that the laboratory may have space for a suitable number of flammable storage cabinets. Per the Uniform Fire Code, quantities greater than 10 gallons of flammable liquids must be stored in a flammable liquid storage cabinet, unless safety cans are used. No more than 25 gallons of flammable liquids in safety cans may be stored outside a flammable liquid storage cabinet.
      • Flammable liquid storage is not allowed below grade or near a means of egress, per the Uniform Fire Code.
      • Flammable storage cabinets should not be vented unless there is a significant odor or vapor control concern.
      • Laboratories using corrosive liquids should have ample storage space low to the floor, preferably in low cabinets, such as under fume hoods.
      • Allow space for the variety of waste collection containers needed. Depending on the laboratory, these may include laboratory trash, broken glass, sharps, recyclable containers, used oil, medical waste, and/or radioactive waste.
      • Laboratories using compressed gases should have recessed areas for cylinder storage and be equipped with devices to secure cylinders in place.
      • All laboratories should have storage space for supplies and combustible materials, e.g., boxes of gloves, spill kits, boxes of centrifuge tubes, etc.

      Laboratory Ventilation (top)

      • Laboratory ventilation rates should ensure 8-10 air changes per hour minimum for occupied spaces and 6 air changes per hour minimum when unoccupied.
      • Bypass style fume hoods should be used. Auxiliary air hoods should not be used.
      • Fume hoods should have recessed work surfaces to control spills.
      • The location of fume hoods, supply air vents, operable windows, laboratory furniture and pedestrian traffic should encourage horizontal, laminar flow of air into the face of the hood, perpendicular to the hood opening. Hoods should be placed away from doors and not where they would face each other across a narrow isle.
      • Hoods may have a face velocity of 100-125 linear feet per minute with the sash fully open or at its standard configuration (e.g., at the stopper height).
      • Each hood must have a continuous monitoring device, such as a magnehelic gauge. The device should display either air velocity or static pressure, rather than only an audible alarm.
      • Supply air vents should be placed away from or directed away from fume hoods to avoid interference. Air velocity caused by supply vents should not exceed 25 feet per minute at the face of the hood.
      • Noise from the fume hood should not exceed 65 dBA at the face of the hood.
      • Use hard ducting for the positive side of exhaust ducting for all internal (penthouse) fans to prevent contaminant leakage into work areas.
      • Fume hood exhaust ducts must not contain fire dampers.
      • Unless otherwise specified (e.g., clean rooms), air pressure in the laboratory should be negative with respect to the outer hallways and non-laboratory areas.
      • Consider the need for vented chemical storage areas or cabinets for chemicals with low odor thresholds.
      • Semi-conductor and other hazardous gases (e.g., silane, hydrogen fluoride, chlorine, etc.) must be placed in vented gas cabinets
      • Hoods for perchloric acid require stainless steel construction and a wash-down system and a dedicated, isolated fan.
      • Hoods requiring filters (such as those for some radioisotopes or biological materials) should be designed and located such that filters may be accessed and changed easily.
      • Provisions should be made for local exhaust of instruments, gas cabinets, vented storage cabinets or other operations requiring local ventilation.
      • Single vertical sliding sashes are preferred over horizontal or split sashes.
      • Debris screens should be placed in the ductwork leading from the hood.

      Emergency Equipment (top)

      • Laboratories using hazardous materials must have an eyewash and safety shower within 100 feet or 10 seconds travel time from the chemical use areas.
      • Drench hoses support, but do not replace, safety showers and eyewashes.
      • Eyewashes and safety showers should have plumbed drains.
      • Eyewashes and safety showers should be standardized at least within a laboratory building.
      • Flooring under safety showers should be slip-resistant.
      • Safety showers may have privacy curtains, particularly in large laboratories or teaching laboratories.
      • Fire extinguishers, safety showers and eyewashes should be conspicuously labeled, particularly if recessed.
      • Fire extinguishers appropriate for the chemicals and equipment in use should be placed near the entrance of each laboratory, mechanical and electrical room.
      • Some chemical operations (e.g., distillation hoods) may benefit from hood fire suppression systems.
      • Windowless laboratories and environmental chambers should have emergency lighting.
      • Alarm enunciator panels should be descriptive of the area where the alarm has activated.

      Materials Handling (top)

      • Loading docks should be equipped with dockboards and should have enough room to maneuver pallets safely.
      • Cryogenic liquid tanks should be placed in such a manner that their controls could not accidentally be manipulated and such that they may be secured to prevent unauthorized access.
      • Cryogenic liquid tanks should be placed away from below grade areas where dense vapors may collect and away from glass doors or windows.
      • A phone should be placed near any loading area.

      Utilities (top)

      • Utility shut-off controls should be located outside the laboratory.
      • Laboratories should have an abundant number of electrical supply outlets to eliminate the need for extension cords and multi-plug adapters.
      • Electrical panels should be placed in an accessible area not likely to be obstructed.
      • Ground fault circuit interrupters should be installed near sinks and wet areas.
      • Environmental chambers where evacuation or other alarms cannot be heard should be equipped with strobe lighting or additional alarms.
      • Central vacuum systems should not be used, since they are vulnerable to contamination. Local vacuum pumps are preferable.
      • All vacuum lines should have cold traps or filters to prevent contamination.
      • Chilled water loops should be available for equipment in need of cooling. Loops help to avoid excessive wastewater.
      • Laser laboratories should have an emergency cut-off switch installed near the entrance of the laboratory to turn off the laser remotely. Many lasers require water-cooling systems requiring ground-fault circuit interrupters.

      Other (top)

      • Laboratories using highly toxic gases should be equipped with alarmed vapor sensors, preferably with automatic shutdown systems.
      • Gas lines from highly toxic gases should use coaxial tubing for double containment.
      • Animal care and use areas must meet Association for Assessment and Accreditation of Laboratory Animal Care International standards.
      • Laboratories classified as Security Protection Level 2 (high value equipment or security-sensitive materials) may require additional security measures.

      Established September 10, 1999 by Environmental Health and Safety. Contact Robin Izzo at or 258-6259 for any questions or concerns.

      Health and Safety Design Considerations
      Project Checklist

      Chemical, Biological or Radioactive Material Use


      Chemical Type Consideration Section
      General Solvent resistant coved flooring B
          Possibly need ventilated storage C
          Solid, sturdy shelving for storage C
          Space for chemical waste storage C
          Plumbed, conspicuously labeled eyewash and safety shower within 100 feet or 10 second traveling distance E
          Fire extinguishers mounted near entrance of work or storage area and conspicuously labeled. E
      Flammable Liquids More than 10 gallons in a lab needs flammable liquid storage cabinet C
          Storage not allowed below grade C
      Corrosives Storage in low cabinets or shelves C
      Perchloric Acid Stainless steel hood with washdown system D
      Radioactive materials Physically separated eating and drinking areas A
          Separate radioactive material areas from other areas A
          Space for radioactive waste storage C
      Biological Agents Handwashing sinks with elbow or electronic controls B
          Space for medical waste storage C
      Highly Toxic Chemicals Handwashing sinks with elbow or electronic controls B
      Highly Toxic Gases Vented gas cabinet D
          Coaxial tubing H
          Alarmed vapor sensors H


      Equipment Type Consideration


      Autoclave Adequate space for use, maintenance and materials storage 


          Drainage to minimize flooding


      Fume Hood Bypass style. No auxiliary air hoods.


          Located to minimize cross-drafts and turbulence


          Face velocity 100-125 linear feet per minute 


          Continuous monitoring device


          No fire dampers in exhaust ducts


          Debris screen


          Single vertical sash


      Distillation Hood Hood fire suppression system


      Environmental Chamber Emergency lighting


          Visual or audible local alarm if regular alarm system cannot be heard inside the chamber


      Cryogenic Liquid Tanks Controls secured or located to prevent accidental opening


          Not below grade or near glass doors or windows


      Lasers Ground-fault circuit interrupters near water-cooling systems


          Consider use of chilled water loop


          Carbon dioxide fire extinguishers, rather than dry chemical extinguishers


          Emergency cut-off switch at entrance


      Equipment needing cooling Chilled water loops


      Vacuum lines Local pumps preferred over central systems


          Cold traps or filters to prevent contamination



      Appendix E: Best Practices in Laboratory Safety Management
      Appendix C: Chemical with High Acute Toxicity