Clean and dirty cabin air filter for car
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.
Most cabin air filters have a pleated filtering medium that looks like paper but is a more complex material made of natural and/or synthetic fibers, allowing them to trap most contaminants. In many designs, the passage of air over the filter creates an electrostatic charge that helps attract and trap smaller particles. Quality filters may have several layers that support the filtering medium and offer different types and degrees of filtration.
As the quality of a cabin air filter increases, so does its price. A basic filter may cost $15; while a premium original equipment part may be $50 or more. Standard cabin air filters are typically around 98% efficient at trapping particulates and the majority of contaminants, but not the smallest particles of mold, spores, soot, and tobacco smoke.
High-Efficiency Particulate Air (HEPA) cabin air filters can trap even finer particles. One major supplier claims their premium HEPA cabin air filters have a filtration efficiency of 99.97% at 0.3 microns, based on standardized industry testing.
Besides filtering particulates, many cabin air filters are chemically treated with activated carbon that gives them a gray appearance and helps remove a wide variety of odors, like exhaust gas smells. Some cabin air filters supplement carbon with baking soda to neutralize a wider range of smells, including odors from the human body, wet-dogs, and mildew.
There are three factors to consider when determining if your car’s cabin filter needs to be replaced:
- Mileage: Factory recommended intervals for replacing cabin air filters range from 15,000 to 30,000 miles. Ask your auto repair shop or check your auto’s owner’s manual for exact mileage specifications.
- Levels of fine particulate matter: You may need to replace the filter more frequently if you drive in an area that has higher than normal levels of dust, pollen, and other airborne debris.
- Performance: Symptoms of a restricted cabin air filter include reduced airflow through the HVAC system, windows that fog up easily and are hard to defrost, and persistent bad odors. A restricted cabin air filter also places a greater load on the ventilation fan and can shorten its service life.
Cabin air filters are located in the ductwork that delivers outside air to the HVAC system. In some cars, the filter is in the engine compartment near the base of the windshield. In others, it is located under the dash or behind the glove box. Most cabin air filters can be replaced in less than 15 minutes without tools, although some take a little longer and may require removing fasteners that hold the glove box or interior trim panels in place.
There is also good news for some drivers whose cars came without a cabin air filter. To reduce the number of different parts they have to manufacture, many automakers use the same HVAC ductwork on every trim level of a given model. As a result, if your owner’s manual talks about cabin air filter replacement, there is a good chance the car is equipped to accept one, even if a filter was not installed at the factory. Simply follow the replacement instructions to determine whether the ductwork contains the necessary filter housing.