New cars are increasingly equipped with cabin air filters that remove particulates, and sometimes odors, from the air that enters the vehicle through the heating, ventilation, and air conditioning (HVAC) system. Cabin air filters are usually standard equipment on premium models, while other cars make them available as a stand-alone option or part of an option package. Some luxury cars have two or more cabin air filters. The types and sizes of contaminants a cabin air filter can trap vary with the specific filter design. However, a general list includes dirt, dust, leaves, twigs, insects, soot, smog, mildew, pollen, mold, spores, fungi, bacteria, germs, rodent droppings, and other undesirable debris.

A cabin air filter is more than just a way to improve air quality; it can also affect vehicle safety. The Filter Manufacturers Council estimates that 40 million Americans suffer from allergies caused or made worse by airborne particulates. By removing those contaminants, a cabin air filter can reduce or eliminate symptoms such as sneezing, blurred vision, runny nose, and headaches that could distract a driver and result in a collision.