The 501 MERV 15 Equivalent Air Filter helps capture and remove common airborne contaminants and allergy triggers, including particulates associated with tobacco smoke and smog. This replacement air filter is 6 in. thick with a large surface area for capturing pollutants and offering superior filtration to typical 1 in. filters. Filtering out airborne contaminants helps clean the air you breathe and can lower the frequency of cleaning and vacuuming by reducing dust buildup around the house. It also maximizes the lifespan of your heating and cooling systems, which can become inefficient with dust and particle buildup. Equivalent to MERV 15 when performance tested to AHRI 680 Standard using the AprilAire Electronic Air Purifier. Removal efficiency - 89 percent 0.3-1 micron, 95 percent 1-3 microns, and 98 percent 3-10 microns.