The Dirt on Air Purifiers

The name alone can seem reassuring to people who worry about indoor air pollutants, but there's little evidence that air purifiers, or air cleaners, do anything to help improve your health. "Studies have been inconclusive and have shown insufficient research that using them makes an impact on your health," says Janice Nolen of the American Lung Association (ALA). Furthermore, air purifiers only remove small particulate matter--not VOCs or combustion gases--and are ineffective at removing all of the toxins in tobacco smoke from the air. Some ionizing air purifiers have even been shown to add to the problem of indoor air pollution by emitting ozone, an irritant that can exacerbate asthma and decrease lung function.

Nevertheless, associations like the ALA and the American Academy of Allergy, Asthma and Immunology concede that when used to supplement common-sense cleaning and home maintenance, air purifiers can help alleviate some air quality problems, such as dust, pollen and mold spores, as long as you do your research and buy an air purifier that can handle your home's specific pollutants. First you need to determine whether you want a whole-house or room air purifier. Consumer Reports, which rates air purifiers frequently, recommends whole-house purifiers if you have forced-air heating or cooling systems, that is, systems that use recirculated air rather than air pulled in from the outside. Otherwise, CR tests have determined that room air purifiers will work almost as well.

The best available measure for determining which room air purifier you need is the Clean Air Delivery Rate (CADR) certification system established by the Association of Home Appliance Manufacturers. The CADR is an efficiency standard applied to stand-alone units that measures the number of cubic feet per minute that air purifiers can remove tobacco smoke, pollen and dust when set on "High." The higher the number, the better the cleaning rate. Consumer Reports, which looks at the CADR in their independent tests, considers ratings above 350 excellent and those below 100 poor. Beware, however, of the CADR rating for tobacco smoke removal. No air purifier can remove the gases associated with tobacco smoke; they can only remove small particulate matter that is found in smoke, says Nolen. She adds that large particles from smoke, dog dander or other sources escape air purifiers because they are too heavy to be moved by air and fall to the ground where you must dust, sweep or vacuum them up. CADR certification is a voluntary program and manufacturers pay for the testing themselves.

For product recommendations, see our Air Purifiers Buying Guide.