Replacement HEPA particle filter (2-pack) for AOS-2071. Replace every 12 months. These filters efficiently capture harmful particles such as pollen, dust and spores that are up to 100,000 times finer than a human hair. After just a short period of use, these filters remove up to 99.97% of harmful particles from the air. Total filter effective area - 35 sq ft (3.2 m2).