The military designed the first HEPA filter in the 1940s for use in the Manhattan Project, when safety from free-floating nuclear material was a primary concern. Today, HEPA air purifiers are very widely used to remove dust, pollen, mold, bacteria, and other airborne particles. They are perhaps the most tried-and-true method of air cleaning to date. The best part about HEPA air purifiers is that they emit no byproducts or secondary pollutants such as ozone.

The Department of Energy continues to be the sole certifying body for all HEPA filters. The DOE has strict standards. All HEPA filters must be able to catch at least 95% of particles as small as 0.3 micrometers. If you are shopping for HEPA air purifiers, beware of