Carbon/Potassium Permanganate Cartridge Replacement Air Filter for PM-400 Keep your Miracle Air PM-400 not included air purifier working to keep the air cleaner around you. The 15 pound* activated carbon and potassium permanganate cartridge air filter is the third stage filter of the Miracle Air PM-400 air purifier not included . This air filter removes odors, gases, chemical, toxins and vapors i.e. formaldehyde, benzene, toluene, xylene, etc. . Carbon potassium permanganate air filters need to be inspected and replaced annually. Replace every 1 to 5 years depending on the environment where the Miracle Air PM-400 is used. *Each filter contains 12 pounds of activated carbon and 3 pounds of alumina potassium permanganate. This item ships from a separate warehouse and may require extra time for delivery.