High Efficiency Particulate Air Filters are the most efficient air filters commercially available. They are used in cleanrooms and other applications requiring ultra-clean air: semiconductor, electronics, pharmaceutical manufacturing, food processing, hospitals, and labs. Every AstroCel® filter is individually tested before shipment to assure it meets rated efficiency and resistance. AAF HEPA filters are available in a variety of efficiencies - from 99.97% tested on .3 µm particles to 99.99995%, and higher, tested on .1 to .2 µm particles. All filters are available scan tested.