Multiple levels of cleaning include HEPA, Pre-Filter and a Charcoal layer to help improve indoor air qualityHEPA Filter captures 99% of dust and allergens, pet dander, mold spores and plant pollens.Charcoal filter reduces common odors from pets, smoking and cooking.Replacement filter for GermGuardian Air Purifier Model AC4100, AC4150PCA and AC4150BLCAOnly one single combination filter needs to be replaced every 6-8 months depending on the use of the product; IMPORTANT: Use genuine Guardian Technologies replacement parts to maintain product performance and warranty.