The OdorStop OSAP2FIL is a H13 true HEPA replacement filter for the OSAP2B and OSAP2W Air Purifiers. It can remove contaminants to a level of 0.3 microns. Buyer's beware: some HEPA filters are only remove up to 85% of contaminants. The OSAP2FIL is a high efficiency filter and should be changed every 6 months - frequency may vary depending on conditions.