Commercial grade H13 True HEPA Filter captures up to 99.95 percent of particles as small as 0.1 microns, including allergens, such as pollen, dust, pet dander, and smoke. Antimicrobial treatment provides built-in protection from the growth of odour and stain-causing micro organisms. Compatible with Fellowes AeraMax PRO AM3, AM3S, AM4 and AM4S Air Purifiers. Replace the HEPA Filter approximately every 12 months, depending on usage conditions, in order to ensure that the Air Purifier remains effective. Pack of 2 H13 True HEPA Filters.