Question: The STAO Safe on Science document (2011) indicates that only class 1 and class 2 lasers are recommended for use in high school science classes. Many of the documents that I have examined indicate that Class 3A (old classification), now called Class 3R (new classification) is also safe unless viewed through an optical device. I respectfully request that the safety committee re-examine this issue, and include Class 3R in the recommendation.
Answer: The Safety Committee Response: Laser Classification: There are currently 7 hazard classes of lasers. As the class number increases, the danger from direct and indirect viewing of the laser beam increases. 1. Direct Viewing: While direct viewing may seem obvious, the eye must be in the path of the beam. High school activities typically position students at 90′ to the direction of the beam, as they watch it travel through lenses, reflect off mirrors, or form interference patterns when the beam enters a diffraction grating.
Looking at a beam from the side as it travels through the air is not direct viewing and will not result in eye damage. 2. Indirect Viewing: Indirect viewing occurs through specialty devices that employ mirrors, lenses, and filters for detecting the laser beam. Class 1, 1M, 2, and 2M lasers have a visible light beam, and are safe under normal conditions of use. The blink reflex will protect users from retinal damage if the light beam is accidentally shone in their eyes. However, viewing the beam through a microscope, binoculars, telescope or other optical equipment may cause immediate damage to the eye. Class 3R lasers can be either visible or invisible.
They are also safe under normal conditions, and the blink reflex for a visible beam will protect users from damage if the beam is accidentally shone in their eyes. However, viewing the beam through a microscope, binoculars, telescope or other optical equipment may cause immediate damage to the eye. Class 3B and 4 are more powerful lasers. They can cause eye damage when viewed directly or by reflection from a matte or mirrored surface. Class 4 lasers also cause skin damage and may be a fire hazard. The Ontario Ministry of Labour requires that a Laser Safety Officer be appointed and trained to oversee the use of these types of lasers. Safety goggles specific to the laser wavelength must be worn when using these lasers.
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