Did you know that you need more than one air filter to purify household air? Most indoor pollutants fall into two categories: harmful particulate matter like smoke, pollen, dust, tobacco smoke, and gaseous matter like paint fumes and vapors from cleaning products. Each type of impurity responds to different filters. The HEPA filter tends to work best at removing particulates, while the carbon filter is necessary for trapping gaseous pollutants. Install both for dual protection.