Viruses, airborne toxins, dust mites, pet dander in the air—it's enough to make you want to hold your breath or, if manufacturers have their way, buy an air purifier. Some of the 30 models we tested were quiet and effective; two did so little that we judged them Don't Buy: Performance Problem.
Some air purifiers can remove or reduce smoke, dust, and pollen from your home. The Whirlpool AP51030K, $300, and Hunter 30547, $260, worked very well even at lower, quieter fan speeds. That's important because most people put portable purifiers in bedrooms or living rooms. Other models, such as the Airgle 750, $800, and FilterStream AirTamer A710, $280, cleaned very well only at the highest, noisiest speed. But no air purifier alone will relieve asthma and allergy symptoms, and if you don't have respiratory problems, you probably don't need one.
We focused on portable and whole-house models that use filters because they don't produce ozone, a respiratory irritant that can aggravate asthma and cause permanent lung damage. We also tested two widely available purifiers that rely on electrostatic precipitation. (For more information on the various technologies used in purifiers, see Guide to purifier types and technologies.) And we even tested one that claims to transform plants—yes, plants—into effective air cleaners.
Here's what else we found:
With no fan to aid airflow, the LightAir IonFlow 50F, $400, was about as effective at removing dust and smoke in our tests as having no purifier at all, though it didn't emit ozone. We judged the Light-Air a Don't Buy: Performance Problem. The Oreck AIR12GU, $400, "electronically charges dust, allergens, and germs and pulls them out of the air like a magnet," its maker claims. But the Oreck was only slightly better than the LightAir at removing dust and smoke on its lowest speed and only fair on its highest speed—and it produced low levels of ozone.
The most effective ones are usually professionally installed and cost hundreds. One do-it-yourself filter, the Web Plus Adjustable Electrostatic 20x25x1, $17, is claimed to trap dust and pollen but was ineffective in our tests. Unlike the more effective do-it-yourself filters we tested, it was only marginally better than a standard furnace filter, which is meant only to protect equipment, not purify air. The Web Plus is also a Don't Buy: Performance Problem.
Some claims by manufacturers have prompted government responses. The Federal Trade Commission last year ordered several companies to stop marketing purifiers as being effective against the H1N1 virus. The Environmental Protection Agency cautions that air cleaners outfitted with ultraviolet light are unlikely to kill bacteria and mold because they won't be in contact with UV light long enough to have any effect. And Florida's attorney general warned residents that using an ozone generator would make wiring problems associated with defective Chinese drywall worse, not better.