Quantification of ozone levels in indoor environments generated by ionization and ozonolysis air purifiers

Indoor air purifiers are advertised as safe household products for health-conscious individuals, especially for those suffering from allergies and asthma. However, certain air purifiers produce ozone (O-3) during operation, either intentionally or as a byproduct of air ionization. This is a serious concern, because O-3 is a criteria air pollutant regulated by health-related federal and state standards. Several types of air purifiers were tested for their ability to produce ozone in various indoor environments at 40-50% relative humidity, including office rooms, bathrooms, bedrooms, and cars. O-3 levels generated by personal wearable air purifiers were also tested. In many cases, O-3 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. Simple kinetic equations were obtained that can predict the steady-state level of O-3 in a room from the O-3 emission rate of the air purifier and the first-order decay rate of O-3 in the room. The additivity of O-3 levels generated by independent O-3 generators was experimentally demonstrated.