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:
