Honeywell 50000293 003 20 x 20 Post Filter 2 Filter Pack Titanium Apatite Photocatalytic Filters any HVAC technician can install Anti Mold any HVAC technician can install it in under an hour The second stage combines a pleated particulate filter with activated carbon — capturing finer visible particles while adsorbing odors and VOCs (volatile organic compounds) Please refer to your unit's Owner's Guide for instructions on changing your air cleaner filter and resetting the indicator These high efficiency charged post filters boost the efficiency of any Honeywell electronic air cleaner with negligible effect on pressure drop