What is a HEPA filter?

9/20/2021 (Permalink)

1. What is a HEPA filter?

HEPA is a type of pleated mechanical air filter. It is an acronym for "high-efficiency particulate air [filter]" (as officially defined by the U.S. Dept. of Energy).  This type of air filter can theoretically remove at least 99.97% of dust, pollen, mold, bacteria, and any airborne particles with a size of 0.3 microns (µm). A micron is one-millionth of a meter or approximately 1/25000 of an inch. The diameter specification of 0.3 microns responds to the worst case; the most penetrating particle size (MPPS). Particles that are larger or smaller are trapped with even higher efficiency. Using the worst-case particle size results in the worst-case efficiency rating (i.e. 99.97% or better for all particle sizes). Source: https://www.epa.gov/indoor-air-quality-iaq/what-hepa-filter-1