A tanning bed, also known as a sunbed, is a machine used to produce an artificial tan by imitating the sun's ultraviolet (UV) radiation. A typical tanning bed emits 95% UVA and only 5% UVB, although some new models produce only UVA. Because UVB rays are considered carcinogenic, manufacturers have come up with a series of filters that seem to eliminate UVB rays and make the beds safer.
A typical bed features anywhere from 27 to 60 fluorescent lamps, which are coated with a phosphor blend and emit about 150 watts each. Some models have metal-halide gas lamps. These types of beds, known as filter beds or high pressure beds, produce a much higher level of UVA rays, which are regulated by a cobalt glass filter.
A tanning bed can be a stand-up or a lie-down model. Most beds nowadays have lamps all around, rather than on the top and bottom only, making for an even tan. In the last few years, home models have become available. They sell for under 3,000 US dollars (USD), as opposed to 25,000 USD for a professional model, and are usually more compact, with as little as 16 low-pressure lamps.
Each bed has a recommended maximum exposure time, measured in minimal erythemal doses (MED). This is usually about 20 minutes for most beds, but it can be lower for the new models, which are much stronger. Tanning salons are regulated by the Food and Drug Administration (FDA) and must meet some standards, such as providing special goggles to protect the eyes from radiation and posting signs with the "Recommended Exposure Schedule."
A tanning bed works by stimulating melatonin production in the skin, pretty much in the same way that the sun does. However, the sun produces a deeper tan that lasts longer, partly because the exposure time is much shorter in a tanning bed, making the tan more superficial. There is great controversy regarding the safety of these machines. Some argue that because a tanning bed controls the amount of ultraviolet radiation emitted, it is safer than tanning outdoors. In any case, moderation is the key.