Applied Optics Laser Safety: Simple Information About Laser Classes

Lasers are generally classified and controlled according to the following criteria:

Class I / 1 lasers - Lasers that are not hazardous for continuous viewing or are designed in such a way that prevent human access to laser radiation. These consist of low power lasers or higher power embedded lasers (i.e., laser printers).

Class II / 2 visible lasers (400 to 700 nm) - Lasers emitting visible light which because of normal human aversion responses, do not normally present a hazard, but would if viewed directly for extended periods of time. (like many conventional light sources).

Class IIa / 2R visible lasers (400 to 700 nm) - Lasers emitting visible light not intended for viewing, and under normal operating conditions would not produce a injury to the eye if viewed directly for less than 1,000 seconds (i.e. bar code scanners).

Class IIIa / 3R lasers - Lasers that normally would not cause injury to the eye if viewed momentarily but would present a hazard if viewed using collecting optics (fibre optics loupe or telescope).

Class IIIb / 3b lasers - Lasers that present an eye and skin hazard if viewed directly. This includes both intrabeam viewing and specular reflections.
Class IIIb lasers do not produce a hazardous diffuse reflection except when viewed at close proximity.

Class IV / 4 lasers - Lasers that present an eye hazard from direct, specular and diffuse reflections. In addition such lasers may be fire hazards and produce skin burns.

Here is another description, paraphrased from the CORD course: "Intro to Lasers".

(On-line version at: Course 1 - Intro to Lasers. See the section: On-Line Introduction to Lasers.) It relates the laser classifications to common laser types and power levels:

Class I / 1 - EXEMPT LASERS, considered 'safe' for intrabeam viewing. Visible beam.
Maximum power less than 0.4 uW. This will not cause damage even where the entire beam enters the eye and it is being stared at continuously.

Class II / 2 - LOW-POWERED VISIBLE (CW) OR HIGH PRF LASERS, won't damage your eye if viewed momentarily. Visible beam.
Maximum power less than 1 mW for HeNe laser.

Class IIIa / 2R - MEDIUM POWER LASERS, focused beam can injure the eye.
HeNe laser power 1.0 to 5.0 mW.

Class IIIb / 3b - MEDIUM POWER LASERS, diffuse reflection is not hazardous, doesn't present a fire hazard.
Visible Argon laser power 5.0 mW to 500 mW.

Class IV / 4 - HIGH POWER LASERS, diffuse reflection is hazardous and/or a fire hazard.

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