• Class 1- Exempt Lasers

• Class 2- Low Power Visible Lasers

• Class 3- Medium Power Lasers and Laser Systems

• Class 4- High Power Lasers and Laser Systems

• Classification

Lasers are classified according to their potential to cause biological damage.  The pertinent parameters are:

• Laser output energy or power
• Radiation wavelengths
• Exposure duration
• Cross-sectional area of the laser beam a the point of interest

In addition to these general parameters, lasers are classified in accordance with the accessible emission limit (AEL), which is the maximum accessible level of laser radiation permitted within a particular laser class.

The ANSI standard laser hazard classifications are used to signify the level of hazard inherent in a laser system and the extent of safety controls required.  These range from Class 1 lasers (which are inherently safe for direct beam viewing under most conditions) to Class 4 lasers (which require the most strict controls).  The laser classifications are described below:

Class 1-Exempt Lasers

Class 1 laser cannot, under normal operating conditions, produce damaging radiation levels.  These lasers must be labeled, but are exempt from the requirements of the Laser Safety Program. A laser printer is an example of a Class 1 laser.

Class 1M lasers cannot, under normal operating conditions, produce damaging radiation levels unless the beam is viewed with an optical instrument such as an eye-loupe (diverging beam) or a telescope (collimated beam).  This may be due to a large beam diameter or divergence of the beam. Such lasers must be labeled, but are exempt from the requirements of the Laser Safety Program other than to prevent potentially hazardous optically aided viewing.

Class 2-Low Power Visible Lasers (top)

Class 2  lasers are low power lasers or laser system in the visible range (400 - 700 nm wavelength) that may be viewed directly under carefully controlled exposure conditions.  Because of the normal human aversion responses, these lasers do not normally present a hazard, but may present some potential for hazard if viewed directly for long periods of time.  A continuous wave (cw) HeNe laser above Class 1, but not exceeding 1 mW radiant power is an example of a Class 2 laser.

Class 2M  lasers are low power lasers or laser system in the visible range (400 - 700 nm wavelength) that may be viewed directly under carefully controlled exposure conditions.  Because of the normal human aversion responses, these lasers do not normally present a hazard, but may present some potential for hazard if viewed with certain optical aids.

Class 3-Medium Power Lasers and Laser Systems (top)

Class 3 lasers are medium power lasers or laser systems that require control measures to prevent viewing of the direct beam.  Control measures emphasize preventing exposure of the eye to the primary or specularly reflected beam.

Class 3R denotes lasers or laser systems potentially hazardous under some direct and specular reflection viewing condition if the eye is appropriately focused and stable, but the probability of an actual injury is small.  This laser will not pose either a fire hazard or diffuse-reflection hazard.  They may present a hazard if viewed using collecting optics.  Visible CW HeNe lasers above 1 mW, but not exceeding 5 mW radiant power, are examples of this class.

Class 3B denotes lasers or laser systems that can produce a hazard if viewed directly.  This includes intrabeam viewing or specular reflections.  Except for the higher power Class 3b lasers, this class laser will not produce diffuse reflections.  Visible cw HeNe lasers above 5 mW, but not exceeding 500 mW radiant power, are examples of this class.

Class 4-High Power Lasers and Laser Systems (top)

A high power laser or laser system that can produce a hazard not only from direct or specular reflections, but also from a diffuse reflection.  In addition, such lasers may produce fire and skin hazards.  Class 4 lasers include all lasers in excess of Class 3 limitations.

Classification (top)

Commercial lasers are classified and certified by the manufacturer.  When a commercial laser is modified or when a new laser is constructed in the laboratory, it is the responsibility of the principal investigator to classify and label the laser per the ANSI Standard.  EHS can assist in determining the appropriate classification.  See Table A for a summary of typical laser classifications.