Lasers are like any other bright light source in being a hazard to sight. Just as people quickly learn not to stare directly at the sun, they should never look directly into a laser.
Class 1 and Class 2 laser devices aren't directly harmful - the laser inside might be, but the device has cutouts to prevent it operating. Class 3b does permanent damage to sight and Class 4 can start a fire.
Unfortunately laser classification tends to fall under different authorities. In the US there are ANSI, OSHA, CDRH(part of FDA) and the NRPB. Not surprisingly, other countries may have different regulations.
Class 1
| Laser with a visible beam considered safe for direct viewing. A warning may still suggest avoiding prolonged viewing. Maximum power less than 0.4 uW. Alternatively the laser incorporated in a device may be hazardous but is made safe by cutout switches. |
| Class 2 | Low powered visible beam won't damage the eye if viewed momentarily. Maximum power less than 1mW for HeNe laser. |
| Class 3a | Medium powered lasers, a focussed beam can injure the eye on prolonged viewing or if viewed with collecting optics such as a telescope. Maximum power between 1 mW and 5 mW for HeNe. |
| Class 3b | Medium powered lasers, a focussed beam will injure the eye but does not normally pose a fire hazard although some materials may ignite at the higher power levels. Maximum power between 5 mW and 500 mW. A mechanical shutter closes the aperture when it is not correctly positioned. |
| Class 4 | High power lasers over 500mW. A focussed or diffuse reflection will damage eyesight and do pose a hazard of skin burns and fire. |
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© Graham Huskinson 2010
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