IRVINE, Calif. - Ionizing air purifiers have been getting attention these days, both in the general media and in a study from the University of California, Irvine. "Quantification of Ozone Levels in Indoor Environments Generated by Ionization and Ozonolysis Air Purifiers," by Nicole Britigan, Ahmad Alshawa, and Sergey A. Nizkorodov, was reported on by MSNBC and in the Journal of the Air & Waste Management Association.

"Indoor air purifiers are advertised as safe household products for health-conscious individuals, especially for those suffering from allergies and asthma," the report's abstract begins. "However, certain air purifiers produce ozone (O3) during operation, either intentionally or as a byproduct of air ionization. This is a serious concern, because O3 is a criteria air pollutant regulated by health-related federal and state standards."

The researchers said they tested the ability of several types of air purifiers to produce ozone in various indoor environments at 40-50 percent relative humidity, including office rooms, bathrooms, and bedrooms. "In many cases, O3 concentrations were well in excess of public and/or industrial safety levels established by U.S. Environmental Protection Agency, California Air Resources Board, and Occupational Safety and Health Administration," the researchers reported.