Some popular air cleaners actually pollute the air with ozone, a known lung irritant. Ozone is a molecule composed of three oxygen atoms; it’s the same molecule that makes up the ozone layer of our upper atmosphere. Stratospheric ozone is a good thing because it protects us from dangerous UV rays; however, ozone in the air we breathe is harmful.

The Environmental Protection Agency (EPA) states that “relatively low amounts can cause chest pain, coughing, shortness of breath, and throat irritation. Ozone may also worsen chronic respiratory diseases such as asthma and compromise the ability of the body to fight respiratory infections.”

Ion generators are sold as air cleaners, but they actually pollute the air; they emit ozone, which can irritate the lungs and even cause asthma. On top of that, despite their popularity, ionic air cleaners do not work very well. They create charged particles (ions) and emit them into the surrounding air. These ions combine with impurities (like dust) in the air, forcing the impurities to cling to a nearby surface. Consequently, ion generators often produce dirty spots on nearby walls and floors because they do not eliminate impurities; ion generators simply force impurities to cling to a surface (in the same way that static electricity can make a sock cling to a shirt). HEPA air purifiers, on the other hand, actually trap pollutants inside the filter.

The EPA tells us: “Available scientific evidence shows that, at concentrations that do not exceed public health standards, ozone is generally ineffective in controlling indoor air pollution.”

The American Lung Association (ALA) agrees that “ozone is a potent lung irritant and exposure to elevated levels is a contributor to the exacerbation of lung disease; it is especially dangerous for persons with asthma and other chronic lung diseases, children, and the elderly.”

The ALA does not suggest the use of ozone generators because “ozone generators, negative ion generators, and certain other electronic air cleaners that are not listed by the FDA, or cannot otherwise prove that their ozone emission levels are lower than 0.05 ppm, may produce levels of ozone recognized as unsafe for humans and are not recommended for use in occupied spaces because of the risk of generation of ozone.”

Consumer Reports (1992), the National Institute of Occupational Safety and Health (1995), and the U.S. EPA (1995) concluded that tabletop and room unit ozone generators are not effective in improving indoor air quality.

The EPA advises the public to “use proven methods of controlling indoor air pollution,” which include eliminating or controlling pollutant sources, increasing outdoor air ventilation, and using proven methods of air cleaning, such as HEPA air purifiers.