Environmental Health & Safety

Laboratory Safety Unit

Laser Safety for Research and Teaching Laboratories

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4. LASER CLASSIFICATIONS

Lasers and laser systems are grouped according to their capacity to produce injury. Specific controls are required for each group. Lasers manufactured after August 1, 1976 are classified and labeled by the manufacturer. Information on the label includes the laser class, the maximum output power, the pulse duration (if pulsed), and the laser medium or emitted wavelengths. The American National Standard for Safe Use of Lasers modified the classification of lasers in 2014 to:

1. Class 1: Low-power lasers and laser systems that cannot emit radiation levels greater than the Maximum Permissible Exposure (MPE). Class 1 lasers and laser systems are incapable of causing eye damage. These lasers are exempt from control measures. The maximum exposure duration for a Class 1 laser is assumed to be no more than 30,000 seconds except for infrared systems, with wavelengths greater than 0.7 um, where 100 seconds shall be used. This does NOT apply to service periods requiring access to Class 1 enclosures containing higher-class lasers.
2. Class 1M: These lasers and laser systems are considered incapable of producing hazardous exposures during normal use unless the beam is viewed with an optical instrument (collecting optics).  These lasers are exempt from control measures other than to prevent potentially hazardous optically aided viewing. The maximum exposure duration is assumed to be no more than 30,000 seconds except for infrared systems, with wavelengths greater than 0.7 um, where 100 seconds shall be used.
3. Class 2: These low-power lasers or laser systems operate in the visible spectrum (400-700 nm) and are incapable of causing eye damage because of the aversion response (0.25 seconds). Previously rated Class 2 lasers that emit visible radiation less than 0.4 mW are now classified as Class 1.
4. Class 2M: These low-power lasers or laser systems operate in the visible spectrum (400-700 nm) and are incapable of causing eye damage because of the aversion response (0.25 seconds). However, Class 2M lasers are potentially hazardous if viewed with certain optical aids. Previously listed Class 3A lasers for momentary viewing without optical aids are now classified as Class 2M.
5. Class 3: Medium power lasers and laser systems capable of causing eye damage with short duration (<0.25 seconds) exposures to a direct or specular reflection viewing conditions, but is normally NOT a diffuse reflection or fire hazard. This class is subdivided into 3R and 3B lasers.
1. Class 3R: These lasers or laser systems may be hazardous under some direct and specular reflection viewing conditions if the eye is focused and stable, but the probability of an eye injury is small. These lasers do NOT pose a fire hazard or a diffuse-reflection hazard.
2. Class 3B: These medium-powered lasers or laser systems in the visible or invisible regions may be hazardous under intrabeam (direct) or specular (mirror-like) reflection viewing conditions, but is normally not a diffuse (scattered) or significant skin hazard except for higher power 3B lasers operating at certain wavelength region.
6. Class 4: These high-power lasers and laser systems are capable of causing acute hazards to the eye and skin with short-term duration (<0.25 seconds) exposures to direct, specular reflection, or diffuse reflection beams. Class 4 lasers and laser systems are also capable of igniting flammable and combustible materials even from diffuse reflection. These lasers may produce laser-generated air contaminants and hazardous plasma radiation.
7. It is the responsibility of the PI/Lab Supervisor who operates or supervises the operation of a "fabricated" laser to provide sufficient information to EH&S to verify the classification and labeling of the laser.

Continue to the next section - Laser Hazards

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This page last updated 7/11/2019. Disclaimer.