Tip of the day: How to choose an air purifier

Consumers Union, the nonprofit publisher of Consumer Reports, continues to urge the U.S. Consumer Product Safety Commission to set indoor ozone limits for all air purifiers and mandate performance tests and labels disclosing the results. CU also urges the Federal Trade Commission to investigate air purifier ads to determine the validity of health-related claims.

But if you're set on buying an air purifier, read our latest report "Filtering the claims" and see our Ratings of room and whole-house models (available to subscribers) and keep these points in mind:

Consider a whole-house air purifier. Forced-air heating/cooling systems circulate so much air that they can overwhelm portable purifiers. Whole-house purifiers are a better option. Better products range from $10 to $30 for do-it-yourself filters (shown) to $1,000-plus systems that have to be installed by a pro. The latter are more effective at removing dust and smoke.DIY furnace filters do nearly as good a job of removing dust but aren't as good at removing smoke. Buy a whole-house air purifier with a filter rather than an electrostatic precipitator, which produces some ozone.

Buy a bigger portable model. Portable air purifiers work best at high speeds but are quietest on low. Run the unit on the higher, louder setting when you're not in the room, and turn it down to low when you're nearby. Or buy an air purifier certified for a larger area. We believe a clean-air delivery rate (CADR) above 350 is excellent, and one below 100 is poor. Look for CADR figures with an Association of Home Appliance Manufacturers (AHAM) logo. Only those were confirmed by AHAM.

Avoid ozone generators. Makers of ozone generators often target home users with claims that the devices reduce allergens such as dust, smoke, pollen, germs, and mold.

But our tests found that even at the low everyday settings on some ozone generators, their ozone production quickly exceeded the Food and Drug Administration's 50 parts per billion limit for medical devices. Purifiers aren't considered medical devices by the FDA.

The U.S. Environmental Protection Agency warns that relatively low levels of ozone can cause chest pain and shortness of breath. Ozone might also worsen asthma and compromise the ability of the body to fight respiratory infections. The EPA regulates outdoor ozone levels, but there is no federal agency that regulates indoor levels or air purifiers. California has recently banned the sale of ozone generators for most uses.—Ed Perratore