This certified, genuine Levoit True HEPA Replacement Filter for the AirNow Air Purifier is used to keep your air purifier at its best working condition and capacity. The pre-filter, HEPA filter and activated carbon filter work together to remove 99.9% of dust, pollen, smoke, odor, allergies, mold spores, and pet dander. This filters particles as small as 0.3 microns and larger air pollution of PM 2.5. This filter will not release any strange smell and works to remove unwanted odor and particles. This is perfect for those who are sensitive to the surrounding air or anyone who wants to improve the air quality. Ensure to remove the plastic bag on the filter before running the air purifier. The activated carbon pre-filer should be replaced every 2-3 months. Your air purifier comes with 2 extra pre-filters. The HEPA filter to do its best work, Levoit recommends replacing the filter every 6-8 months - the filter may need to be replaced sooner or later depending on the air quality in your area.