Airrex HEPA filtration removes airborne particles down to .3 micron in size with 99.97% efficiency. The Airrex HEPA 2000 provide relief from allergy, asthma, sinus problems, mold spores, pathogens, and chemical irritations. These units are also used in hospital remodels and new construction to reduce air born dust. The Airrex units are excellent in reducing the indoor pollution that have been proven to make us feel sick. The HEPA 2000 unit uses replaceable 1st stage and 2nd stage filters that help extend the usage of the HEPA filter. All replacement parts and filters are available at Airrex USA.