October 2007
How to choose
Don't assume that any air purifier will improve your health. "There's no definitive proof that air purifiers improve air quality
in any way that benefits the health of those with or without allergies or asthma," says Rebecca Bascom, M.D., professor of
medicine at the Penn State medical center's division of pulmonary, allergy, and critical care medicine. The American Lung
Association and medical societies such as the American Academy of Allergy Asthma and Immunology also say there's little evidence
that air purifiers alone will reduce the effect of indoor pollutants for those with asthma or allergies.
See Simple air-cleaning steps for low- and no-cost cleaning methods before buying an air purifier. If you buy one, check our Ratings of room models for top performers. Then keep these points in mind as you shop:
Decide on whole-house or room. Whole-house models are the only sensible choice for forced-air heating or cooling. Room models are the only option for other homes; the best performed at least as well on Low as most others did on High, minimizing noise and energy use.
Choose a type. In past and current tests. electronic-precipitator, or EP, air purifiers have worked best overall and restricted airflow least among whole-house models. They process by which EPs work creates some ozone as a byproduct.
We now believe that air purifiers that emit even small amounts of ozone (less than 50 parts per billion) are not your best choice. Research is increasingly warning against adding ozone to indoor air. But more studies need to be conducted to determine the effects of low-level ozone exposure.
Whole-house filters tend to cost the least up front. But they can cost more than electrostatic precipitators over time, since you usually must replace such filters every one to three months.
Check efficiency. Most room air purifiers are certified by the Association of Home Appliance Manufacturers as part of a voluntary program that includes appropriate room size and clean-air delivery rate (CADR), a measure of cleaning speed on High. We judge CADR above 350 excellent and below 100 poor. Choose a model certified for a larger area than you require for better cleaning at a quieter speed.
Many whole-house filters have a minimum efficiency reporting value (MERV). The top-performing models we tested have a MERV of 11 to 13.
See Simple air-cleaning steps for low- and no-cost cleaning methods before buying an air purifier. If you buy one, check our Ratings of room models for top performers. Then keep these points in mind as you shop:
Decide on whole-house or room. Whole-house models are the only sensible choice for forced-air heating or cooling. Room models are the only option for other homes; the best performed at least as well on Low as most others did on High, minimizing noise and energy use.
Choose a type. In past and current tests. electronic-precipitator, or EP, air purifiers have worked best overall and restricted airflow least among whole-house models. They process by which EPs work creates some ozone as a byproduct.
We now believe that air purifiers that emit even small amounts of ozone (less than 50 parts per billion) are not your best choice. Research is increasingly warning against adding ozone to indoor air. But more studies need to be conducted to determine the effects of low-level ozone exposure.
Whole-house filters tend to cost the least up front. But they can cost more than electrostatic precipitators over time, since you usually must replace such filters every one to three months.
Check efficiency. Most room air purifiers are certified by the Association of Home Appliance Manufacturers as part of a voluntary program that includes appropriate room size and clean-air delivery rate (CADR), a measure of cleaning speed on High. We judge CADR above 350 excellent and below 100 poor. Choose a model certified for a larger area than you require for better cleaning at a quieter speed.
Many whole-house filters have a minimum efficiency reporting value (MERV). The top-performing models we tested have a MERV of 11 to 13.
