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Air Purifiers

Americans spend 90 percent of their time inside, where air typically contains two to five times more pollutants than the outdoors, according to the U.S. Environmental Protection Agency (EPA). Because of all our indoor air quality problems, the EPA ranks indoor air pollution as a high-priority public health risk.

For the purposes of this guide, we looked at portable air purifiers. They're easily moved move from room to room, and they're the only air purifiers rated by Energy Star (see below).

What To Look For

Type of Filter

Portable room air cleaners trap particles in either a high-efficiency particulate air (HEPA) filter, or, for electrostatic models, electrically charged metal collector plates. HEPA filters must be replaced over time, while electrostatic filters are washable. Furthermore, electrostatic filters do produce some ozone as a by-product, and high ozone levels can exacerbate respiratory problems.

Some models also contain carbon filters to eliminate odors, reduce humidity and filter larger particles, but "carbon filters have not been very effective in our tests," CR says. Finally, ionizing air purifiers clean the air by releasing ions into the room, but again, these have been found less effective in product tests than HEPA filters and may produce ozone.

Energy Star Rating

Energy Star rates air purifiers based on their "Clean Air Delivery Rate" (CADR) a measurement established by the Association of Home Appliance Manufactures. The CADR measures the removal of dust, pollen and tobacco smoke and represents the number of cubic feet of clean air a unit delivers each minute. Each purifier must remove dust at a rate of 2.0 square feet of air per watt of power used. Also, all Energy Star-rated purifiers, regardless of filter type, must meet the UL requirement for ozone (50 ppb).

Room Size

You want to be sure you buy a purifier that's suitably sized to your room. A machine that's too large will pose a drain on your energy bill, while one that's too small won't be effective.

Annual Filter Replacement Costs

Operating costs carry just as much weight as upfront costs when it comes to affordability. Whether purchasing one of the models on our Product Comparison page or one of your own personal choice, be sure to ask about replacement filter costs.