Ozone vacuum-ultraviolet (VUV) ozone generators, employ a light source that generates a narrow-band ultraviolet light, a subset of that produced by the Sun. The Sun's UV sustains the ozone layer in the stratosphere of Earth. UV ozone generators use ambient air for ozone production, no air prep systems are used (air dryer or oxygen concentrator), therefore these generators tend to be less expensive. However UV ozone generators usually produce ozone with a concentration of about 0.5% or lower which limits the potential ozone production rate. Another disadvantage of this method is that it requires the ambient air (oxygen) to be exposed
Sun tanning tanning and UV radiation exposure, either from the sun or from indoor tanning. Production of vitamin D is essential for human health. Moderate exposure (avoiding sunburn) to UV radiation provides benefits such as increased vitamin D, as well as other possible benefits that are still being studied. Several tanning activators have used different forms of psoralen, which are known to be photocarcinogenic. Health authorities have banned psoralen since July 1996. Tanning has gone in and out of fashion. In the United States and Western Europe before about the 1920s, tanned skin was associated with the lower classes, because they worked