Air filters are devices which use fibrous materials to remove solid contaminates from the air, such as mold, pollen, bacteria, and dust. Vehicles use two different types of air filters: automotive cabin air filters and internal combustion air filters.
The cabin air filter cleans pollen, dust, and other contaminates from the climate control air flow (air conditioning and heating). If working properly, the filter makes sure that the air circulating inside the car is free from the harmful elements. If these filters are not replaced periodically, AC performance can be negatively affected. In extreme cases, a clogged filter can even pose a potential health risk for the driver and any passengers. It's recommended that the cabin air filter be changed every 12,000 miles, or at least once a year, whichever comes first.
The internal combustion air filter prevents contaminates from entering an engine's cylinders, which could cause extra mechanical wear as well as contaminating the engine's oil. If the air flowing though the engine isn't adequately filtered, the effects can lead to excessive fuel consumption and low engine power, eventually requiring expensive repairs.