ANSI Z136 standard requires specification according to optical densities (OD) only. ANSI also allows a Nominal Hazard Zone (NHZ) to be determined by the laser safety officer (LSO). Outside of the NHZ, diffuse viewing eyewear is allowed. Most Asian countries refer to these ANSI regulations. Australia has adopted new laser safety regulations that are based on the European laser safety regulations (EN 207/EN208).
In Europe there is a second criteria to be taken into consideration -- the power/energy density (i.e. the power/energy per area = per beam area). 'Diffuse viewing' condition is not allowed and laser safety glasses must protect against a direct laser exposure. Protection due to Optical Density alone is not sufficient when the material of the eyewear cannot withstand a direct hit. The following regulations are called the 'norm,' but in fact they are legal requirements and enforceable. Other legal requirements (e.g. the regulations for industrial safety as well as the medical equipment regulations) refer to them as well.
Laser eye protection products require direct hit testing and labeling of eye protectors with protection levels, such as D 10600 L5 (where L5 reflects a power density of 100 MegaWatt/m2 as the damage threshold of the filter and frame during a 10 seconds direct hit test at 10,600nm). Filter and frame must both fulfill the same requirements. It is not acceptable to select glasses according to Optical Density alone. The safety glasses must be able to withstand a direct hit from the laser for which they have been selected for at least 10 seconds (CW) or 100 pulses (pulsed mode).
This norm refers to glasses for laser alignment. They will reduce the actual incident power to the power of a class II laser (< 1 mW for continuous wave lasers). Lasers denoted as class II are regarded as eye safe if the blink reflex is working normally. Alignment glasses allow the user to see the beam spot while aligning the laser. This is only possible for visible lasers (according to this norm 'visible lasers'(defined as being from 400 nm to 700 nm). Alignment glasses must also withstand a direct hit from the laser for which they have been selected, for at least 10 seconds (CW) or 100 pulses (pulsed mode).
Requires that laser safety eyewear provide sufficient optical density to reduce the power of a given laser to equal to or less than the listed Maximum Permissible Exposure levels (MPE). It allows specification according to optical densities in extreme situations, but recommends the use of EN 207 with a third party laser test. In neither standard is a nominal hazard zone allowed; the only consideration is protection against the worst-case situation such as direct laser radiation.
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