Lasers have been categorized into 4 hazard classes based on the accessible emission limits or AELs. These limits indicate the class of the laser and are listed in EN 60825-1 and the American National Standards ANSI Z136.1 for Safe Use of Lasers. The AEL values for the
laser classes are derived from the medical MPE (Maximum permissible exposure) values. The MPE values specify the danger level for the eye or the skin with respect to laser radiation. Since November 2001 the laser classes are defined as listed below.
Summary of Laser Classes
Class
Concept
Comment
1
The radiation emitted by this laser is not dangerous.
No need for protection equipment
1M
Eye safe when used without optical instruments, may not be safe when optical instruments are used.
No need for protection equipment, if used without optical instruments.
2
Eye safe by aversion responses including the blink reflex.
No need for protection equipment
2M
The light that can hit the eye has the values of a class 2 laser, depending on a divergent or widened beam, it may not be safe when optical instruments are used.
No need for protection equipment, if used without optical instruments.
3R
The radiation from this laser exceeds the MPE values (MPE: maximum permissible exposure). The radiation is max. 5 x AELs of class 1 (invisible) or 5 x of class 2 (visible). The risk is slightly lower than that of class 3B.
Dangerous to the eyes, safety glasses are recommended.
3B
Old class 3B without 3R. The view into the laser is dangerous. Diffuse reflections are not considered as dangerous.
Dangerous to the eyes, safety glasses are obligatory
4
Old class 4 Even scattered radiation can be dangerous, also danger of fire and danger to the skin
Personal safety equipment is necessary (glasses, screens)
