HEPA Filters were developed by the Atomic Energy Commission during World War 2 to remove radioactive dust from plant exhaust. HEPA filters (High Efficiency Particulate Air) filters are now the primary filtration systems for electronic clean room assembly, hospital surgery rooms, bio-engineering, pharmaceutical processessing, and any application where maximum reduction or removal of sub micron particulate is required. Because air from HEPA filters is free of 99.97% of all particulate down to 0.3 microns in size (including bacteria, fun gal and other opportunistic microbiological organisms) it is rapidly coming into many medical applications such as isolation of patients under treatment involving immunological isolation, care for bum victims, and orthopedic surgery.

Generally, HEPA filters belong to the "interception" family of filters and are variously referred to as "absolute", "super interception", and so on. Such filters have a deep bed of randomly positioned fibers (made of glass, commonly called micro glass), in which the total bed depth (thickens of media) is very large in comparison to average fiber diameter and effective pore or free-path cross-section. Even though the media may be only 1/16 thick, this is an enormous distance compared to the 0.3 to 1.0 micron diameter of the fibers. The passages through which air must flow are not straight, but are very tortuous, with many twists and turns. As particulate impact on the fibers and adhere to them, the passages become smaller and filter efficiency goes up.

The HEPA filter maintains it efficiency over its two to four year life. It is 99.97 percent efficient by particle count as a size of 0.3 microns, which is 1/75,000 of an inch, or 1/300 the diameter of a human hair. It becomes more efficient both above and below the 0.3 micron particle size. HEPA requires no cleaning or maintenance to maintain this efficiency. In fact HEPA filters actually become more efficient over time filtering out smaller and smaller particles since as the filter gets filled less large particulate matter can pass through them.

Because all respirable particulates including bacteria, fungi and other minute airborne contaminant's are trapped in the HEPA filter, the use of HEPA filtration, when properly applied, will significantly eliminate or reduce the health effects of airborne contaminates on the respiratory system.

It is for this reason, that Austin Air HEPA filters are recommended by more allergist's and medical professionals than any other filter system available.