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 |
|---|---|---|
| Class 1 |
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) |
N/A |
| 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).