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The Germicidal Nature Of UV Light |
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Ultraviolet rays have shorter wavelengths than visible light. A wavelength,
the distance between the crests of two waves, is often measured in units called
nanometers. A nanometer (nm) is a billionth of a meter, or about 1/25,000,000
inch. Wavelengths of visible light range from about 400 to 700 nm. Ultraviolet
wavelengths range from about 1 to 400 nm and are beyond the range of visible
light. UV Fact SheetAbout Ultraviolet (UV) Light Used for Air Disinfection What is UV or ultraviolet light? Ultraviolet light is part of the spectrum of electromagnetic energy generated by the sun. The full spectrum includes, in order increasing energy, radio waves, infrared, visible light, ultraviolet, x-rays, gamma rays and cosmic rays. Since UV is not visible, it is technically not "light", but use of the term "ultraviolet light" is so widespread that, it will be used here. Most sources of light generate some UV. For air disinfection, UV is generated by electric lamps that resemble ordinary fluorescent lamps. What is germicidal UV? This is UV of a specific type (253.7nm wavelength) known to kill airborne germs that transmit some infections from person to person within buildings. Germicidal UV is aimed at the upper room air so that only airborne microbes are directly exposed. Room occupants are exposed only to low levels of reflected UV - levels below that known to cause eye irritation. Germicidal UV has been used safely and effectively in hospitals, clinics and laboratories for more than 60 years. UV does not prevent transmission of infections (e.g. colds) by direct person to person contact. Is UV harmful? We are all exposed to the UV in sunlight. UV exposure can be very harmful, or harmless, depending on the type of UV, the type of exposure, the duration of exposure, and individual differences in response to UV. There are three types of UV:
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