Class 3R

Class 3R lasers are higher powered devices than Class 1 and Class 2 and may have a maximum output power of 5 mW or 5 times the Accessible Emission Limit (AEL) for a Class 1 product. The laser beams from these products exceed the maximum permissible exposure for accidental viewing and can potentially cause eye injuries.

This Class, which was introduced into the British Standard with Amendment 3, replaces the former Class 3A and the low power part of Class 3B. Class 3A had the additional requirement that the irradiance of the laser beam should not exceed 25 W m ^-2. The effect of the irradiance limit was to restrict the power admitted to a fully dilated human eye (taken as a 7 mm acceptance aperture) to 1 mW. As such, accidental exposure to a Class 3A laser beam was no more hazardous than accidental exposure to a Class 2 laser beam. An individual accidentally exposed would be protected from injury by their natural aversion response. Class 3A laser pointers were, however, potentially hazardous when viewed with an optical aid such as binoculars and were therefore not suitable for the general consumer.

To satisfy the irradiance criteria, a laser pointer with an output power greater than 1 mW would have to produce an expanded beam to reduce the irradiance below 25 W m ^-2. As the characteristic feature of a laser pointer is the small spot produced by the narrow beam, expanding the beam area to satisfy the irradiance criteria effectively destroys this useful property. It was therefore extremely unlikely that a laser pointer with a power output in excess of 1 mW would satisfy the Class 3A AEL criterion. Therefore, in general, laser pointers were either Class 1, Class 2 or Class 3B products. The former Class 3B laser pointers, which did not exceed 5 mW, are now Class 3R.

The American Standard ³ does not have the Class 3A irradiance criteria previously specified in the British Standard. Therefore, a correctly classified American Class IIIA laser pointer would have become Class 3B device when classified against the British Standard. The use of Roman numerals should indicate that the product has been classified in accordance with the American Standard. In practice, examples occur where an inappropriate 3A label has been substituted for the IIIA label. All of the American IIIA laser products will now be Class 3R under the British Standard.

Examples of Class 3R products include some laser pointers and some alignment products used for home improvement work.