Do Air Purifiers Work?

They can help, within limits. The EPA says portable air cleaners, also known as air purifiers or air sanitizers, are designed to filter the air in a single room or area, and that while portable air cleaners and HVAC filters can reduce indoor air pollution, they cannot remove all pollutants from the air.

The EPA says most portable air cleaners are rated by their clean air delivery rate, or CADR, and that the higher the CADR, the more particles the air cleaner will remove and the larger the area it can serve, with the rating typically measured at the highest speed. To size one, it says to multiply the length and width of the room and compare the result with the maximum recommended room size on the packaging, to choose a unit sized for a larger area if ceilings are above 8 feet, and to consider multiple air cleaners for a space larger than any product will serve.

Particles and gases need different filters. The EPA says that to filter gases, you should choose a portable air cleaner with an activated carbon filter or another filter designed to remove gases, and notes that the CADR rating system is for particles only.

Ozone is not the answer. The EPA says available scientific evidence shows that, at concentrations that do not exceed public health standards, ozone is generally ineffective in controlling indoor air pollution. The California Air Resources Board says that since 2010, all indoor air cleaners sold in or shipped to California must meet ozone emission and electrical safety standards, including an ozone emission concentration below 0.050 parts per million, and that amendments effective October 1, 2020 required electronic in-duct air cleaners to be certified too, after a phase-in that ended October 1, 2022.