Cabin Air Filter: The Unseen Automotive Filter – UnderhoodService

Cabin Air Filter: The Unseen Automotive Filter

A new cabin air filter is something many motorists need, but often don't know it. The cabin air filter (CAF) is not a well-known or well-publicized filter. Close to 90% of late-model cars and trucks now come factory-equipped with a cabin air filter, but the original filters in many of these vehicles have never been changed!

A new cabin air filter is something many motorists need, but often don’t know it. The cabin air filter (CAF) is not a well-known or well-publicized filter. Close to 90% of late-model cars and trucks now come factory-equipped with a cabin air filter, but the original filters in many of these vehicles have never been changed!

Depending on the type of filter, recommended replacement intervals can range from once a year or every 15,000 miles up to 3 years or 30,000 miles. Driving on dusty roads would obviously require more frequent filter changes, yet many motorists are totally unaware their vehicle has a cabin air filter let alone how often it should be changed or how to replace it.

One reason why cabin air filters are so neglected is because the filter is often hard to find.  It may be located under the cowl cover at the base of the windshield or inside the HVAC (Heating Ventilation and Air Conditioning) plenum behind the glove box or under the dash. Accessing the filter often requires some disassembly, and some filters have to be folded and unfolded to fit in place.

The filter’s location can usually be found in the vehicle owner’s manual along with the recommended service intervals.

Some vehicle manufacturer’s (notably GM) have been inconsistent in their use of CAFs. The filters have been used since the 1980s, but on some GM trucks, the filter was discontinued when certain models were updated or changed from one year to the next.

In some cases you also will find a cabin air filter listing for a vehicle application that has a slot for a filter but was not originally equipped with a filter.

How important is the cabin air filter? A plugged cabin air filter can restrict airflow through the heater, defroster and air conditioner.  The filter prevents dust, pollen and other contaminants (down to 1 to 3 microns in size and smaller) from entering the passenger compartment. For allergy sufferers, this is a good feature to have.

Filters that have a layer of activated charcoal also can trap odors and other pollutants, making for a more pleasant driving experience in heavy traffic or when passing hog farms, soybean processing plants and other sources that generate nasty odors. Activated charcoal can even reduce the levels of carbon monoxide and oxides of nitrogen from the exhaust of other vehicles, which can be high in heavy traffic.

The concentration of these pollutants can often be several times higher inside a vehicle than outside, which can affect driver reaction time and alertness.  So regular CAF replacement can also have a safety benefit.

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