FEATURES * Compatible with APH260 Air Purifier and APH320 Smart WiFi Air Purifier only. * True HEPA Technology: Fine pre-filter, true HEPA filter, and activated carbon filter work together to capture harmful pollutants in indoor air. * Best Choice for Allergies: It removes 99.97% airborne particles as small as 0.3-micron, such as dust, pollen, bacteria, mold spores, pet dander, smokes, and VOCs. * Replacement Alert: When the PM2.5 light turns RED and keeps flashing, this is a reminder to check and change the filter, which is supposed to be every 6-8 months depending on its condition. To reset the replacement alert, press the FAN and TIMER button simultaneously and hold for 3 seconds.