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. Use the On This Page menu (left) to jump to categories and arrow at bottom of page to return to the top.  

Improper Shelving

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.
  • Ensure that shelving materials are compatible with the chemicals that will be stored on them.
  • Be sure to check the shelf load capacity before using any storage cabinets or shelving units.


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.
  • 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.

Chemical Burns

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. 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

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

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 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 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

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.

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.

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 electropherisis 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.

  • 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).