From:Gary Jones(email@example.com )
Date:Fri, 12 Dec 2003 14:54:06
From CCOHS's (Canadian Centre for Occupational Health and Safety) Health and Safety Report at www.ccohs.ca
Gary Fighting the fluorescent flicker
Headaches, eyestrain and general eye discomfort. These are three common workplace issues with fluorescent lights, and more specifically, the flicker of the lights. The health effects of fluorescent lights may not be the top priority of every health and safety manager, but a little attention and knowledge could go a long way to a healthier workforce.
A little background: North American electrical current runs at 60 cycles per second. In essence, the power is turning on and off 120 times per second, which, in turn, flashes lights 120 times each second. Almost all people can see lights flashing on and off up to about 50 flashes per second. The flicker usually blends into a continuous light at 60 flashes per second. That's especially true with incandescent lights because the filament inside the light bulb doesn't cool quickly enough to produce the flicker. But fluorescent lights, which use ballasts to control its electrical supply, are more of a problem. Although humans cannot see fluorescent lights flicker, the sensory system in some individuals can somehow detect the flicker, leading to headaches, eyestrain and discomfort.
Some types of ballasts reduce flicker considerably. New, energy-efficient electronic ballasts take the regular power supply and convert it to a much higher frequency. The resulting flicker frequency is so high that the human eye cannot detect any fluctuation in the light intensity - essentially making the lights flicker-free. An added benefit is that electronic ballasts produce less hum than that emitted by other kinds of ballasts. According to a study in Lighting Research and Technology, the use of high frequency electronic ballasts (20,000 Hz or higher) dropped complaints of eyestrain and headaches by more than 50 per cent compared to regular fluorescent lights with magnetic ballasts. The study also found that there tended to be fewer complaints of headaches among workers on higher floors compared to those closer to ground level suggesting that workers exposed to more natural light experienced fewer health effects.
There are more options. Replace bulbs on a scheduled basis. Old bulbs tend to flicker more and they are not as bright Ensure that all parts of the light fixture, especially the ballast, are functioning properly When replacements are needed, upgrade to fluorescent lighting that uses electronic ballasts