The Aprilaire 213 furnace filter is a MERV 13, pleated, expandable air filter that is a direct replacement filter for the 4200, 3210, 2210, and 1210 Aprilaire air cleaners. Aprilaire recommends you change the 213 filter every 9 to 12 months, depending on the air quality of your home. For example, if you have smokers or multiple pets in your home, you may have to change the filter more frequently. The Aprilaire 413 filter traps and permanently removes over 90% of pollen, mold, pet dander, dust, dust mites, and other airborne allergens/pollutants. It also removes up to 95% of tobacco smoke!