A High Efficiency Particulate Air (HEPA) filter is a specialized filter capable of trapping 99.97 percent of all airborne contaminants greater than 0.3 microns in size. The purifier's fan draws air through the HEPA filter, removing dust, pollen, mold spores and other allergens from the air.
A HEPA filter must be changed regularly to maintain its effectiveness. Over time, particles will build up in the filtration media, reducing its ability to filter the air. The lifespan of a filter varies according to use and the environment, but in most cases HEPA filters require replacement every 6 to 12 months. In some cases, HEPA filters are paired with a charcoal pre-filter to help trap larger contaminants and extend the life of the unit.