This Genuine Miele Certified HEPA Exhaust Filter #SF-AH 50 combines a Certified HEPA Filter with a thin layer of Activated Charcoal to provide simultaneous HEPA filtration and trapping of unpleasant odors. By meeting the stringent "HEPA 12" specification, it is ideal for allergy and asthma sufferers. This filter should be replaced every 12 months with typical household use.