Airborne transmission of infectious agents resulting in disease has been well-documented. There has been renewed interest in applying engineering controls to remove or inactivate causative agents. Engineering controls include direct source control using local exhaust ventilation, maintenance of negative pressure differences between isolation/treatment rooms and adjacent areas, dilution and removal of contaminated air via mechanical ventilation, in-room air filtration, ultraviolet germicidal irradiation (UVGI), and using respiratory protective equipment. These controls are designed to reduce the concentration of infectious agents within the local environment, to protect those who come into close contact with infectious persons, and to prevent spreading of infectious agents. For upper-room air UVGI, germicidal lamps are suspended from the ceiling or attached to the walls; the bottom of the lamp is usually shielded or louvered to direct radiation upward above a predetermined height. The objective of this configuration is to inactivate airborne infectious agents in the upper part of the room, while minimizing radiation exposure to persons in the lower part of the room.

Inactivation in this context means the loss of the ability to replicate and form colonies. Commercially available germicidal lamps contain mercury vapors under low pressure that emit nonionizing electromagnetic radiation in the UV-C wavelength range, 100-290 nm, with about 90% of the total spectral power emitted at 254 nm. ozone air purifier nzUVGI that penetrates to microbial DNA may cause damage sufficient to interrupt cell replication.alen air purifier ratings My research group has completed studies evaluating the effectiveness of upper-room air UVGI to inactivate bioaerosols. oreck air purifier replacement cellUpper-room UVGI has been shown to inactivate airborne bacteria at significant rates and it has been shown to be effective in controlling a number of airborne biological contaminants.  

Some of our published papers are below: Xu, P., Peccia, J., Fabian P., Martyny, J.W., Fennelly, K.P., Hernandez, M., and Miller, S.L. 2003. Efficacy of ultraviolet germicidal irradiation of upper-room air in inactivating airborne bacterial spores and mycobacteria in full-scale studies. Atmospheric Environment, 37: 405-419. Xu, P., Kujundzic, E., Peccia., J., Schafer, M., Moss, G., Hernandez, M., and Miller, S.L. 2005. Imapact of environmental factors on efficacy of upper-room air ultraviolet irradiation for inactivating airborne Mycobacteria. Sci. Technol., 39: 9656-9664.Furnace Filters and UV Air Purifiers Try a furnace filter before investing in a room air purifier When it comes to air purification, experts suggest trying whole-house options, such as furnace filters, before making a big investment in a stand-alone air purifier. Filtrete filters get the most positive feedback from both owners and in professional reviews. These filters come in a variety of sizes and filtration levels, from a 600 microparticle rating (MPR) up to 2,400 MPR.

Filtrete filters vary in price depending on size and the level of filtration, from about $10 to $25 per filter. Owners say the Filtrete filters are highly effective, and many report a noticeable reduction in their allergy and asthma symptoms after using these filters with their home forced-air heating and air-conditioning systems. All of The Filtrete filters draw positive feedback. We saw the most for the Filtrete Healthy Living 1550 Air Filter (Est. $30 each and up). The biggest benefit to using a furnace filter, besides being able to purify your entire home with a single purchase, is that they don't contribute any additional noise beyond what your furnace creates. Most furnaces recommend using filters anyway, but using a Filtrete Healthy Living 1550 is an additional step for removing allergens that can cause respiratory problems in asthma sufferers and worsen the symptoms of allergies. UV technology isn't yet practical for home air purification The problem with ultraviolet (UV) air purifiers, or combination units that include UV light bulbs, is that the science isn't conclusive.

In one six-year study published in 2003 by the U.S. Centers for Disease Control and Prevention, UV lamps installed in the ceiling of a hospital room (not in an air cleaner) inactivated tuberculosis-like bacteria in the room. In a 2003 study published in the British medical journal The Lancet, germicidal UV lights installed in an office ventilation system significantly reduced workers' breathing problems and overall sickness. However, most home versions are ineffective, according to both the EPA and the Federal Trade Commission (FTC). "Typical UVGI [ultraviolet germicidal irradiation] cleaners used in homes have limited effectiveness in killing bacteria and molds," the EPA says. "Effective destruction of some viruses and most mold and bacterial spores usually requires much higher UV exposures than a typical home unit provides." The problem is primarily because air flows in and out of an air purifier, so it's not in contact with the UV light long enough for it to effectively kill any bacteria, and without a filter, these units won't actually remove small particles from the air.

For now, it's not clear whether UV air purifiers are worth the extra expense over a good HEPA unit -- and none of our sources highly recommends them. In fact, we found no recommendations among our review sources for any air purifiers using ultraviolet technology. While many turn to air cleaners and air purifiers as a first step in reducing indoor allergens and odors, the EPA and other experts instead suggest those as a last resort. The first steps, they say, should be to control sources of allergens and to adequately ventilate your living spaces. Some strategies -- such as removing a beloved pet -- might not be practical or desirable, but others are relatively simple and can be surprisingly effective. One, for example, is to use a dehumidifier to help reduce both mold spores and dust mites, which flourish as humidity levels go up. For more ideas, see the list of things to try at the Asthma and Allergy Foundation of America web site. Prev3 Best Air PurifiersAir Purifiers and OzoneCheap/Small Air PurifiersBuying GuideOur SourcesNext