The indoor air pollution solution. The Homedics TotalClean Replacement Hepa-Type Filter features 360-degree Hepa-type filtration that removes up to 99% of airborne allergens as small as 0.3 microns. Its built-in prefilter traps larger particles and its activated carbon filter reduces household odors. Replace every 12 months with normal usage for optimal performance of Homedics TotalClean 5-in-1 Tower Air Purifiers, Ap-T20, Ap- T20WT.