In short, it helps catch those airborne contaminants as they circulate through your house. Air has to flow through the filter as your furnace and air conditioner work. Anything bigger or more harmful than air will get caught in its fibers. It’s an easy way to ensure high indoor air quality standards. Just be sure to replace your filter every one to three months. Otherwise, those contaminants will build up on the filter and block airflow, which not only harms your air quality but also puts more stress on your comfort systems, which could lead to a breakdown.