Classification of Lasers
In recognition that all lasers and laser system do not pose the same degree of risk, a classification system was developed to categorize these systems depending on their potential to cause biological damage. Although a variety of classification standard exist depending upon the area of application (ex. manufacturing vs application) the ANSI standard is the general accepted standard. The seven classes define the risk of damage associated with exposure to the laser beam, and range from Class 1 (no potential damage) to Class 4 (high degree of potential damage). Each will be briefly described below.
Class 1 - not known to be able to cause biological damage |
| Class 1M - incapable of producing hazardous exposure conditions during normal operation unless the beam is viewed with an optical instrument such as eye-loupe (diverging beam) or a telescope (collimated beam) |
| Class 2 - ocular hazard exists when chronic viewing occurs - limited to visible lasers (either continuous wave or repetitive pulsed) - normal aversion of the eye sufficient to prevent injury - emit above Class 1 level but less than 1 milli Watt radiant power |
| Class 2 A - should now be treated the same as Class 1 designation applied to lasers which are “not intended for viewing” i.e., supermarket laser scanner - based upon 1000 second exposure - upper power limit is 4.0 micro Watts. |
| Class 2M - limited to visible lasers (either continuous wave or repetitive pulsed) - potentially hazardous if viewed with certain optical aids |
| Class 3A - now called Class 3R unless the beam diameter exceeds 7 mm, in which case they could be Class 1M or 2M - intra beam hazard exists for ocular injury but not a serious skin hazard - intermediate power lasers ( 1-5 milli Watts, continuous wave) - permitted to exceed the power limit of Class 2 by five times - often have a expanded beam such that no greater than 1 milli Watt is enter a fully dilated pupil (7 mm) - depending upon reference standard may include invisible and visible lasers |
| Class 3R - intra beam hazard exists for ocular injury but not a serious skin hazard - intermediate power lasers ( 1-5 milli Watts, continuous wave) - permitted to exceed the power limit of Class 2 by five times - often have a expanded beam such that no greater than 1 milli Watt is enter a fully dilated pupil (7 mm) - depending upon reference standard may include invisible and visible lasers |
| Class 3B - both ocular and skin damage possible when direct exposure occurs (including mirror reflections) - scattered reflection not usually considered dangerous, unless laser operating at upper power limit and the beam is viewed at a close distance. - may be visible or invisible lasers but cannot produce greater than 500 milli watts of continuous wave power |
| Class 4 - ocular or skin damage is possible through direct or indirect exposure, risk of fire - high power lasers ( greater than 500 milli watts continuous wave) |