Air cleaners make claims like "capture 99 percent of allergens and irritants," "remove allergens like dust, pet dander and pollen," healthier, fresher air." Consumer Reports tested 26 portable air cleaners to see how well they work.
Testers pump contaminants into a controlled chamber, dust, as well as smoke. Some of the models tested were slow and to removed the contaminants and not terribly effective. The three poorest performers: Hamilton Beach TrueAir 0483, Hoover model WH10600 and Holmes HAP1200-U.
Consumer Reports says also stay away from electrostatic purifiers because they can emit ozone, which can aggravate allergies and asthma.
And be aware, even the best air cleaner isn't going to be enough if you're not very proactive about removing contaminants like vacuuming, dusting, making sure the rooms are adequately ventilated. Those things are actually much more important than just using an air cleaner.
If you still want an air purifier, Consumer Reports says opt for one that uses filters to clean the air. Consumer Reports recommends the Honeywell HPA300for $250. It's relatively quiet and excels at removing dust, pollen and smoke.
Consumer Reports also tested whole-house filters for homes heated and cooled with forced-air. They replace the standard filter in a forced air system. The 3M Filtrete 1550 for about $30 is very good at removing dust and smoke and is one of the least expensive tested. Like many whole-house filters it will need to be installed by a professional.
More free information on buying an air purifier and ridding your home of pollutants is available at http://www.ConsumerReports.org/cro/air-purifiers/buying-guide.htm