HEPA is an acronym for High Efficiency Particulate Arresting (or sometimes Air). HEPA filters use glass fibres to filter particulates out of air. They are incredibly effective and a good HEPA filter will remove 99.97% of particles greater than 0.3 microns in size. To help quantify that number, a human hair's diameter is 300 times too large to penetrate a HEPA filter. The use of a True HEPA filter will contribute to your families health by greatly removing dust, dander, mold spores and other irritating particulates from the air. There are alot of wannabe HEPA filters on the market, make sure yours is a True HEPA.