Hunter 30917 Replacement Filter for HEPAtech Air Purfiers Aftermarket Hunter HEPAtech Replacement Filter Fits Hunter models 30027 and 30028. Filter 1 is a pre-filter that removes large dust particles, lint, and hair from the dirty air Filter 2 is the sub-micron filter that captures 99.7 % of all airbore particles as small as .1 microns from the air Filter 3 is the activated charcoal filter that absorbs and helps eliminate cooking odors, musty air, tobacco odors, and pet related odors as it freshens the air