Nordic Pure 8x20x1 Pure Baking Soda pleated AC / furnace filters are made of electrostatically charged baking soda media equivalent to a MERV 8 rating. Our Pure Baking Soda filters help control, absorb and neutralize odors from pets, smoking, cooking and other undesirable smells. This filter does double duty to ensure the cleanest air in your home, gently removing strong smells, allergens, dust, mold spores, pollen and pet dander. Nordic pure air filters prohibit the growth of mold and bacteria on the filter itself. For maximum odor control, we recommend that you replace your air filter every 30-90 days.