This highly effective True HEPA filter helps to purify the air by capturing allergens and pollutants such as pollen, dust, mold, pet dander and smoke. These allergens and pollutants 0.3 microns and larger passing through the filter are captured to help maximize comfort and freshness. With Holmes brand technology, you can live in harmony with nature for a serene home environment. For best performance, change filter every 12 months.