The genuine Aprilaire 501 replacement air filter media is effective in the reduction of up to 99% of airborne pollutants inside your home or business. Pollen, mold and spore-sized particles that can trigger asthma are easily captured in addition to bacteria-sized organisms that can make you and your family sick. The Aprilaire 501 is an accordion style filter with a MERV 10 rating that benefits from SelfSeal technology to eliminate air gaps that can let contaminants slip through and reenter your air. The Aprilaire 501 replacement air filter is easy to install and removes pollen, dust, pet dander, tobacco smoke and smudging particulates among others. When inahled these contaminants can cause runny noses, headaches, watery eyes, asthma or other serious respiratory problems. Each filter lasts up to a year.