UV Air PurifiersToday UV (ultraviolet) air purifiers are being marketed for residential use. UV purifiers are germicidal lamps, similar to a sun lamp. This type of lamp is classified as U-VC of the ultraviolet spectrum. The most popular are those that are installed into the air ducts of a heating/cooling system, especially near the cooling coil. UV air purifiers alter the DNA of microorganisms, leaving them unable to reproduce. These microorganisms have a short life span, the quickly diminish. In order to be effective, UV lamps have to be within inches of the microorganism, have a certain intensity and exposure time. In most residential air duct applications, it is difficult to position the lamp toward the surface of the cooling coil. Some units are placed in the return air duct. The problem with this applicationis that the air moves so fast there is not enough time for the UV lamp to do it's job. The article "Proper Design of UV Bacteria Control" by James Hart, PE, a typical single bulb unit can not even come close to a 90% kill rate of the bacteria Bacillus. Other types of UV air purifiers use a broad spectrum UV bulb. This type of system does not rely on exposure time of the air with a bulb. It sends friendly oxidizers into the living area that reduce airborne bacteria, mold and viruses up to 99% as well as odors and
VOC's.
The disadvantages are the unit is only effective on coils that are directly in the light path and most bulbs contain mercury without breakage protection a potential heath hazard.
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