Cabin Air Filter

The primary purpose of cabin air filters, located on most vehicles since 2000, is keeping the air inside your vehicle's cabin clean. ... Its job is to filter all of the air that comes through the car's HVAC system to prevent pollutants, such as dust, pollen, smog and mold spores from entering.
Recommended replacement every 12 months or 12,000 miles.
Check for filter replacement if a musty odor emits from the vehicles ventilating system.
Check for filter replacement if the vehicles heating & air conditioning systems exhibits poor performance or efficiency.