Furnace filters are worth a try
There are four main types of console air purifiers on the market. Many air cleaners use combinations of techniques.
HEPA air purifiers use pleated high-efficiency particulate arresting (HEPA) filters to trap particles, along with a fan to pull air through the filter. By a wide margin, reviewers say this type of air purifier is the most effective. These models don't produce any ozone. Because they use fans, they can be noisy, but some are quieter than others.
Electronic ionizers use an electronic process to reverse the charge of particles in the air. The charged particles are then attracted to collection plates in the air purifier, as well as to objects in the room -- such as clothing, walls, floors and furniture. In effect, particles are removed from the air and deposited on your furnishings and clothing. You need to dust and vacuum to actually remove allergens from the room and prevent them from being reintroduced into the air.
Electrostatic air purifiers produce a small amount of ozone, a lung irritant -- the main reason why experts do not recommend them.
Most reviews agree that people with severe allergies, asthma and bronchitis -- who need to control indoor air quality as much as possible -- may benefit from air purifiers, but only when used in conjunction with other allergen-control strategies such as ventilation and daily HEPA vacuuming. These reviews say there's little evidence that air purifiers are effective alone. The Asthma and Allergy Foundation of America takes this stance: "Air filters are worth considering, but not as a solution to your asthma or allergy problems by themselves. The most effective step is to eliminate the source of these allergens and irritants in the first place."
Both the U.S. Environmental Protection Agency (EPA) and the American Lung Association recommend that air purifiers be used as a last resort after allergen source control and ventilation. ConsumerReports.org recommends that you first ban smoking in your house, don't burn wood fires or candles, keep pets out of bedrooms and replace carpets with hard flooring: "In fact, if you don't have allergies, asthma or other respiratory illnesses, you may not need an air cleaner at all."
Whole-house furnace filters aren't air purifiers; they simply replace your regular furnace filter. Filters such as the Filtrete Elite 2200 MPR (Est. $25) do an outstanding job trapping dust and pollen in one leading test, and they do a good job with smoke. Filters need to be replaced every three months. Furnace filters can reduce air flow as they become dirtier, but the Filtrete filters allow very good airflow overall in tests.
We consult professional reviews, such as those from ConsumerReports.org and AllergyBuyersClub.com, and owner-written reviews from Amazon.com and Epinions.com, to determine the best air purifiers based on performance, ease of use, noise levels and the cost of ownership. We also found a number of insightful and thorough reviews by consumers who have severe allergy problems and who have used a variety of different air purifiers in their homes, such as Ed Sherbenou of Air-Purifier-Power.com.