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 sources. These filters come in a variety of sizes and filtration levels, from a 700 to 1,085 microparticle rating (MPR) (better) to a 1,200 to 2,200 MPR (best).
The Filtrete Elite 2200 MPR (Est. $25) is a top-of-the-line filter made by the company, offering excellent dust and pollen filtration for the whole house. The numerical digit assigned to each Filtrete filter indicates its MPR -- the 2200 version offers the highest level of filtration, with the best capability to remove minute particles from the air.
In one professional test evaluated four different do-it-yourself Filtrete filters, the 2200 was the top-rated model and the only model to earn a rating of Excellent for dust and pollen removal. In the same test, the Filtrete Elite 2200 MPR was given a Good rating for its ability to reduce smoke in the air.
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 Elite 2200 MPR is an additional step for removing allergens that can cause respiratory problems in asthma sufferers and worsen the symptoms of allergies.
Filtrete filters vary in price depending on 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 heating and air-conditioning systems.
Filtrete is the predominant manufacturer of furnace filters designed for allergen reduction. In fact, we found few mentions of other air-purification filters, although we did read some positive reviews for the Nordic Pure 20x25x5 Honeywell Replacement AC Furnace Air Filters (Est. $20).
The problem with ultraviolet (UV) air purifiers, or combination units that include UV light bulbs, is that the science isn't conclusive. Studies do show that UV lights installed in hospitals or workplace ventilation ducts can kill germs and reduce illness.
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 that because air flows in and out of an air purifier, 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.