Tanning beds use a special fluorescent lamps (16 to 32 per tanning bed) that creates visible light and ultraviolet light. Like all fluorescent lights, they use a ballast system to limit the electricity going to each lamp, which is most often 100 watts per lamp. The tanning beds use a special acrylic, or clear shield over the lamps. Most clear plastics will block ultraviolet, but this special type of plastic lets most of the ultraviolet light pass through. Most tanning beds also have a cooling fan system, to cool the electronics inside the tanning bed and keep it from getting too hot. All tanning beds have a timer, a device to limit the amount of time the person is exposed to the ultraviolet light. After a few minutes, the timer makes the bed turn off.