Combination Air Purifiers

Alternative air-purifier technology

Some air purifiers combine two or more technologies. One brand, Blueair, uses an electronic precipitator in conjunction with a HEPA-like filter and produces a small amount of ozone (a known lung irritant). It is no longer recommended by reviewers. The electrostatic ionizer applies a negative charge to particles, which then cling to the unit's filter -- and possibly to your furniture, walls and floors.

Ionic air cleaners usually release at least a little ozone, which can irritate lungs and worsen asthma. Although Blueair purifiers have been independently certified by the Association of Home Appliance Manufacturers as emitting less than 50 parts per billion of ozone (the U.S. Food and Drug Administration's upper limit for medical devices), ConsumerReports.org now advises against using electrostatic air cleaners at all: "We now believe that air purifiers that emit even small amounts of ozone (less than 50 parts per billion) are not your best choice," ConsumerReports.org says. "Research is increasingly warning against adding ozone to indoor air." See our Air Purifiers and Ozone section for more information.

Still, some reviews recommend Blueair. The Blueair 650E (*Est. $765) makes Air-Purifier-Power.com's list of the top 10 air purifiers. Although it doesn't use a true HEPA filter, knowledgeable reviewer Ed Sherbenou reports that its combination filter achieves "HEPA-like performance" -- at least in the short term. Its long-term performance "remains, in my opinion, yet to be demonstrated," Sherbenou says. You have to change the filters (*Est. $80) every six months, and there's no prefilter to help keep them clean. By contrast, true HEPA filters usually last for at least a year.

Experts at AllergyBuyersClub.com, a retail website, give the Blueair 650E and its slightly less expensive sibling, the Blueair 603 (*Est. $670), a 4.5-star, "very good plus" rating. Their non-HEPA filters run more quietly and deliver faster air output than a true HEPA -- at least on low speed -- making them an "ideal choice for a large bedroom," according to the AllergyBuyersClub.com. Still, experts there share Sherbenou's concerns about filter life and cost. The Blueair 650E has some convenience features the 603 lacks -- namely, pollution sensors (which automatically boost the fan speed when the air gets dirty), a remote control, an on/off-timer and a filter-change indicator that counts actual days of use (the 603's simply counts down six months). Otherwise, these two air cleaners are very similar.