HEPA Cartridge for Amaircare 2500 and 2550 Portable Air Purifiers Made Prior to 2016 Molded 8 Inch HEPA Filter cartridge for Amaircare 2500 and Amaircare 2550 HEPA Air Purifiers manufactured in 2015 or earlier. Note: this filter has a hole in the middle . HEPA filters last 2- 5 years in most applications if the pre-filters are changed regularly. Replace when inspection shows significant accumulation of dirt and dust. Also replace the HEPA filter when a HEPA air filtration unit has sat idle for more than 3 to 5 days. When moisture collects in HEPA filters, bacteria, mold and viruses can grow. A constant flow of air keeps the HEPA dry and free of such pollutants. Note: Filters are not returnable unless deemed defective after inspection by the manufacturer. Please be careful to order the correct size filter for your air purifier.