Last edit: 10/05/15

Auto Cabin Air Filter

Did you know know that many cars have cabin air filters built into the air conditioning system?

Automotive aftermarket industry surveys have demonstrated that a majority of vehicle owners are unaware of this feature and whether their car can filter cabin air.

Even fewer can find the cabin filter after they are sure their vehicle has one.

These filters have been added to vehicles in the last 20 years without much fanfare.

Marketed on European vehicles since the mid 1980's, cabin air filters began to appear on stateside cars and trucks around 1995.

High projected U.S. growth failed to materialize, but now the cabin air filter is common on American and Asian automobiles.

Cabin filters, as with air filters generally, do not have standardized terminology.

They may be called;

pollen filters,
dust filters,
car air conditioning filters,
ACC filters,
breather filters,
micro filters,
micron air filters,
interior air filters,
and interior ventilation filters.

Many cars are running with dirty, clogged cabin filters.

AC performance will be degraded and inside air filtration will suffer if the filter is not serviced.

Leaves and dirt will clog the filter media, and road grime will turn it pure black in about 12,000 miles.

This is a filter in the incoming air duct of the car's heating ventilating and AC system.

The cabin air filter cleans the air coming into the auto's passenger cabin, collecting pollen and dust.

Since automotive servicing is an area of lower consumer sophistication than the air purifier market in general, rip-offs and exaggerated claims are everywhere.

The question for consumers desiring cleaner air in their cars is fourfold;

Is my auto equipped with a cabin air filtration device, or the hardware to add one?

What features and products are desirable in a replacement filter?

If so, how difficult and costly is it to change or add?

Can I do it myself, or is this a job for professionals?

Where is my Cabin Air Filter?

If you own a 2000 or newer car, it probably has one.

Look first in your auto's owner's manual.

Replacement may also be covered in the owner's manual.

However, many manuals are cryptic at best, shepherding consumers to the high priced service departments where the auto industry makes its real money.

Most dealers will be able to advise you as to whether your vehicle has this filter, AND charge from $50 to $130 to replace it.

But even if these prices seem insignificant to you, I still advise reading on.

Not all replacement filters clean air in a car cabin equally well.

There is no definitive list of car models with or without interior air filtration available to easily answer our first question.

Worse yet, a given model may have the option installed or not, depending on where it was sold or built, which drive train is installed, and other factors.

Many after market filter providers will offer online tools to enter your vehicle data and search for replacement filter media.

Cabin filters are found behind an access panel in the AC duct housing, which may be under the hood or inside the cab. It will generally be on the passenger side.

In the cab, the filter media may often be accessed through or under the glove box.

Under the hood, look on the firewall near the AC plenum box for fasteners which may secure the cabin air filter housing.

Many filters are located under the cowl.

The cowl is the piece of metal trim with vent louvers and windshield wipers sticking through it, just below the windshield.

Some air filter installations require removal of this part.

A common telltale is an asymmetrical 2 piece cowl, with a shorter section on the passenger side.

Replacement Air Filter Features

Like the air conditioning filters commonly found in home furnace ducts, a big function of the automotive interior air filters is protecting heater and AC components.

The reduction of visible dust, which builds up on dashboards, confuses us into believing car cab air is cleaner.

Like the home environmental quality scenario, appearances can be deceiving when things just look clean.

Regular readers of this website already know the next line:

fine lung penetrating particles and volatile organic chemical toxins will go right through many of these filters. They are a good thing, relatively inexpensive air quality insurance, but they are not a real car air purifier.

Two types of cabin air filtration media are offered in the after market: single and multiple stage filters.

A simple single stage particulate filter, maybe just paper, is common in original equipment installations.

Single Stage filter

These one stage filters trap airborne dust, the largest soot, and allergens.

Quality cabin air filters typically use an electrostatic charged fiber mat to capture airborne particles. While better than plain paper, these are not HEPA air filters.

What particle size do they allow through?

Evaluation of car cab air filters begins at about the 10 micron size, with particle filtration efficiency falling rapidly in particle sizes smaller than 3 microns.

Few vendors mention particle efficiency and those that do may say: "The Cabin Air Filter can remove airborne particles that are larger than 3 microns."

Premium products capture particles as small as one micron, but at lower efficiencies, like 30%.

Even the best cannot remove dangerous sub-micron particles. In the scheme of pollution and its impact on the human immune system, 1 micron is boulder-sized.

Many single stage filter media are limp, without stiff edges to hold the filter firmly in the duct or plenum chamber.

This allows airflow to bypass. Sometimes bypassing is intentionally engineered to protect downstream AC components from overload.

Multi-stage filter

A multiple stage car air filter, generally using some activated carbon, reduces toxic gases and odors.

Vendors claim tests have shown carbon monoxide levels are lowered with the multi-stage filter models, but I think this is due to restricted intake rather than the actual ability to remove carbon monoxide.

Multiple stages on premium filters can have progressive size layers like prefilters in room purifiers.

The carbon layer comes near the end. In general, the more stages the better. Better models have reinforced framing and sealed edges.

A premium 5 stage charcoal filter may cost $20 to $35, about double the original equipment replacement.

This is a very small price for filtered air in the cabin.

Filter Replacement Rip-Off

Environmental conditions will determine the useful life of a cabin air filter.

Urban pollution and/or rural dust call for more frequent changes.

Leaf and twig debris will build up in many installations.

Filter replacement is needed when reduced air flow lowers air conditioner, defroster, and heater performance, but filters should be changed long before this is noticeable.

Odors from the ducts may be a signal. Owners' manuals usually recommend replacement every 15,000 miles or so.

Here is a serious issue: installing a cabin filter can be a 20 second job anyone can do as easily as opening and closing a kitchen drawer. Or it can require 30 minutes of a skilled mechanic's time.

Car manufacturers "hide" the cabin air filter in various locations, making them difficult for green mechanics to service.

While many quick-lube operators were slow to adopt to the new cab air filter products, industry journals now report that cabin air filters are their highest profit add-on service.

It's a new version of the old service station low oil scam.

Workers are trained to recognize the car models with the easiest to change cabin media, and to offer an inferior new filter only to drivers of those car models.

The charge is less than a dealer service department, but is exorbitant for the easy job performed.

It is important to get the correct filter for the application, sometimes these operators will substitute loose fitting air filter media.

If you are not the mechanically inclined type, I recommend insisting on premium multi-stage filter media and observing the process to learn how time consuming it really is.

Do-it-yourselfers and shade tree mechanics will have no trouble with 99% of these installations.

A few may require removal of the passenger side windshield wiper assembly.

A cabin air filter mostly protects against outside air infiltration, but cab air quality is determined by emissions inside the cabin as well.

Running the AC on recirculate will help, but is not a complete solution. Many particulates do not enter through the AC system.

I recommend frequent replacement of original equipment cabin filter media, using 5 stage premium aftermarket products.

But don't stop there, consider a car air purifier or running a room purifier in the parked car periodically.

Car Cabin air filters to fit most brands are available at Amazon:

Car Cabin Air Filters at

Make sure the filter is listed to fit your make, model and year.

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