The cabin air filter

The cabin air filter, a feature found on most late-model vehicles, cleans the air that comes into the interior through the heating, ventilation and air-conditioning system. It catches dust, pollen and other airborne material that can make riding in a car unpleasant, particularly if you have allergies or other respiratory problems.
Recommendations on when a cabin air filter should be replaced vary by manufacturer — some say every 12,000 or 15,000 miles, others longer — and how often can depend on how much you drive and where. Check the maintenance schedule in your owner’s manual. If you drive in heavy traffic in an urban area that has poor air quality, you could need to replace The cabin air filter annually or even more often. However, that also could be true in a desert climate where there is a lot of dust to filter out.