Genuine OEM Hunter replacement air filter 30931 for Hunter HEPAtech air purifiers. Fits Models Hunter HEPAtech Air Purifiers: 30212, 30213, 30240, 30251, 30378, 30379, 30381, 30382, 30526, 30527, 30528 Permanently charged HEPAtech filter captures particles as small as 0.1 microns in size. 99.97% effective air cleaning. Captures smoke, pollen, dust, mold spores, pet dander and other irritating allergens. Replace every 4 to 6 months The need to change a filter depends on where and how the air purifier is used and the rate of new particle introduction into the room environment. The replacement filters for Hunters HEPAtech models are designed to last 4 to 6 months under constant use.