Part of the Entertainment Lasers Metanode
Lasers are inherently dangerous at the levels used in entertainment applications. Because of their original designation as medical devices, a division of the Food and Drug Administration called the Center for Devices and Radiological Health (CDRH) controls all lasers. All laser show companies, laser manufacturers, and laser projector manufactures must receive a variance for their product from the CDRH. This variance indicates the fail-safes, interlocks, and other prevention mechanisms used to prevent accidental exposure of the laser beam.
The CDRH divides lasers into four classes. Class I laser pose no danger from laser exposure. Class II laser are not dangerous under momentary exposure. The eye’s blink reflex is fast enough to prevent damage from the lasers. However, Class III lasers are too powerful for even the quarter of a second exposure that the retina would receive before the eye blinked. Class IV lasers not only pose an immediate threat to the eye but also pose a risk of causing burns or fires. However, while all entertainment lasers fall into Class III or Class IV, there have been no serious injuries as a result of accidental laser exposure in the laser entertainment industry’s 30-year history.
Other regulations placed upon entertainment laser production companies regulate how the laser is used in a venue. Clearance rules require minimum setbacks from the farthest extent an audience member can reach to the nearest place the laser beam shines. Typically, a 3-meter setback is required to prevent a spectator from being accidentally exposed to the beam.
Additionally, the CDRH sets the MPE, or Maximum Permissible Exposure
Rule. When lower powered lasers are scanned
very quickly, even laser strengths that would normally cause eye
damage do not because the exposure is so fleeting. Think thousandths of a second. This is why audience scanning
laser shows are possible. The MPE is a measurement of what strength laser the eye can be exposed to for what period of time with no damage. In the US the MPE is set too low for any audience scanning lasers with current technology. Overseas and in Canada
higher MPE rules allow for certain types of audience scanning when additional fail-safes have been installed.
In addition to regulations imposed by the CDRH, the Federal Aviation Administration places additional regulations upon outdoor laser shows. Because of the fear that pilots could be blinded, all outdoor high-powered laser beams must have some sort of termination point. This can be a metal beam stop, nearby buildings, even large dense trees. If the option for terminating the beams does not exist, laser show operators must first receive permission from the FAA for unterminated beams, and then call the local control tower so they can redirect air traffic before every performance.