HEPA filtration technology was developed by the U.S. Atomic Energy Commission to remove airborne radioactive particles. In order to be considered a true HEPA filter, it must be capable of removing 99.97% of particles as small as 0.3 microns, which is 1/75,000 of an inch, or 1/300 the diameter of the human hair. HEPA filters are used in other places such as hospitals and manufacturers’ clean rooms where clean air is absolutely vital. The HEPA filter maintains its efficiency even as the dust cake forms on the filter, the resistance increases, and the air flow rate decreases.