High-Efficiency Particular Air or HEPA filters are specially designed with randomly and loosely interlaced fibers to filter particulate matter that are at least 0.2 microns in diameter. This allows it to remove a large number of air particulates. Some studies say it can actually remove up to 99.9% of impurities in the air, although a more acceptable figure would be somewhere in the range of 99.7 to 99.8 percent.\r