Air purifiers that only produce ozone do not remove allergens from the air. Ozone in large amounts can neutralize strong odors (such as the smoke odor from fire damage), but according to the U.S. Environmental Protection Agency (EPA), it is dangerous for humans. Ozone can damage lungs, worsen asthma and cause other respiratory problems. The U.S. Food and Drug Administration (FDA) limits the ozone production of medical devices to 50 parts per billion (ppb), but manufacturers get around the FDA limit by not claiming their home ozone generators to be medical devices. Some of these units, however, suggest that ozone has health benefits. As of October 2010, the California Air Resources Board has banned all air purifiers that produce ozone levels greater than 50 ppb.
Watch out for manufacturers who disguise ozone by other titles, such as "pure air," "energized oxygen," "saturated oxygen" or "trivalent oxygen." See the EPA's online document "Ozone Generators That Are Sold as Air Cleaners." If you already own an ionizer and are curious about whether it's producing ozone, the not-for-profit International Association of Air Cleaner Manufacturers (IAACM) offers free ozone test kits so consumers can test their own air purifiers for ozone production. Find links to the EPA document and the IAACM free ozone test kits in our Air Purifier Brands and Links section.