The table that follows summarizes potential risks for each laser safety class, according to IEC/EN 60825-1. Safety classes are presented from least dangerous to most dangerous.
|Safety Class||Safe Situation||Unsafe Situation|
For low-emission lasers (≤0.39mW), directly viewing the beam, even for a long time, with the naked eye or with optical instruments
Some designs are also intrinsically safe (i.e., the beam can’t be seen)
|Class 1M||Directly viewing the beam with the naked eye||Directly viewing the beam with optical instruments|
|Class 2||Accidentally viewing the beam with the naked eye or with optical instruments (the blink reflex limits the exposure since the beam is visible)||Intentionally viewing the beam or the magnified beam for longer than 0.25 seconds|
|Class 2M||Accidentally viewing the beam with the naked eye (the blink reflex limits the exposure when the beam is visible)||Intentionally viewing the beam for longer than 0.25 seconds, or accidentally viewing the beam with optical instruments|
|Class 3R||Brief eye exposure (the acceptable time of exposure depends on the wavelength)||Directly viewing the beam, especially with optical instruments|
|Class 3B||Being exposed to diffuse reflections||Eyes accidentally exposed to the direct beam or specular reflections (dangerous) or skin accidentally exposed to the direct beam (small burns)|
|Class 4||Being outside the nominal ocular hazard area (NOHA)||Eyes, skin, or combustible materials exposed to the direct beam, specular reflections, or diffuse reflections|
Note that safety hazards increase as safety classes increase. It's implicit that what's unsafe for a lower class is also unsafe for a higher class (e.g., what's unsafe for class 2 is also unsafe for class 4). It's also implicit that what's safe for a higher class is also safe for a lower class (e.g., what's safe for class 4 is also safe for class 2).