Standard classification for lasers is as follow:
As posted by the Center for Devices and Radiological Health (CDRH) regulation 21 CFR 1040.10 and 21 CFR 1040.11, the standard classification for lasers is as follows:
Class, I laser product
No known biological hazard. The light is shielded from any possible viewing by a person and the laser system is interlocked to prevent the laser from being on when exposed. (large laser printers such as the DEC LPS-40 have a 10mW HeNe driving it which is a Class IIIb laser, but the printer is interlocked so as to prevent any contact with the exposed laser beam, hence the device produces no known biological hazard, even though the actual laser is Class IIIb. This would also apply to CD players and small laser printers, as they are Class I devices).
Class II laser products
Power up to 1 milliwatt. These lasers are not considered an optically dangerous device as the eye reflex will prevent any ocular damage. (I.E. when the eye is hit with a bright light, the eyelid will automatically blink or the person will turn their head so as to remove the bright light. This is called the reflex action or time. Class II lasers won't cause eye damage in this time period. Still, one wouldn't want to look at it for an extended period of time.) Caution labels (yellow) should be placed on the laser equipment. No known skin exposure hazard exists and no fire hazard exists.
Class IIIa laser products
Power output between 1 milliwatt and 5 milliwatts. These lasers can produce spot blindness under the right conditions and other possible eye injuries. Products that have a Class III laser should have a laser emission indicator to tell when the laser is in operation. They should also have a Danger label and output aperture label attached to the laser and/or equipment. A key-operated power switch SHOULD be used to prevent unauthorized use. No known skin hazard or fire hazard exists.
Class IIIb laser products
Power output from 5 milliwatts to 500 milliwatts. These lasers are considered a definite eye hazard, particularly at the higher power levels, which WILL cause eye damage. These lasers MUST have a key switch to prevent unauthorized use, a laser emission indicator, a 3 to 5-second time delay after the power is applied to allow the operator to move away from the beam path, and a mechanical shutter to turn the beam off during use. The skin may be burned at higher levels of power output as well as the flash point of some materials which could catch fire. A red DANGER label and aperture label MUST be affixed to the laser.
Class IV laser products
Power output >500 milliwatts. These CAN and WILL cause eye damage. The Class IV range CAN and WILL cause materials to burn on contact as well as skin and clothing to burn. These laser systems MUST have:
A key lockout switch to prevent unauthorized use Inter-locks to prevent the system from being used with the protective covers off Emission indicators to show that the laser is in use Mechanical shutters to block the beam Red DANGER labels and aperture labels affixed to the laser.
The reflected beam should be considered as dangerous as the primary beam
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