Auto Cabin Air Filter - Does Your Car Have One? |
Did you know that some autos have a cabin air filter, an "air purifier" built into the air conditioning (AC) system?
Aftermarket industry surveys have shown that a majority of vehicle owners are unaware of this feature and whether their car or truck has a cabin air filter.
These filters have been added to vehicles in the last 20 years without much publicity. Placed on European autos in the mid 1980's, cabin air filters began to appear on US cars and trucks around 1995. Now the cabin air filter is common on American and Asian automobiles.
Cabin filters do not have standardized sizing, specifications, technology, or materials. There isn't even standard terminology.
Lots of cars are running with dirty, clogged cabin filters. Air conditioning and heating performance will be degraded and inside air quality will suffer if the filter is not serviced. When there is no pre-filter screen, leaves, twigs, and dirt will clog the filter media. Road grime will turn a white filter ugly black in about 12,000 miles.
Where is my Cabin Air Filter?
If you drive a 2000 or newer car, it probably has a filter.
Replacement is sometimes covered in the owner's manual. However, many manuals are cryptic at best, herding consumers to high priced dealer service departments.
Dealer service desk personnel should be able to advise you as to whether your car has a cabin air filter.
They may charge from $50 to $130 to replace it. But even if these prices seem acceptable to you, please read on. Not all replacement filters purify car cabin air equally well.
There is no list of car models with or without interior air filtration available. Worse yet, a given car model may have the option installed or not, depending on where it was sold or built, which drive train is installed, and other factors.
Filter manufacturer websites will have listings of replacements by make, model, and year. If you don't find your car listed after surfing a couple of these, you probable don't have a cabin filter.
Cabin air filters are often found behind an access panel in the AC duct housing, under the hood or inside the cab. It will often be on the passenger side.
Inside the cab, the filter cartridge may be accessed through or beneath the glove box. Under the hood, check the firewall near the AC plenum box for fasteners which may hold the cabin air filter housing. Many filters are located under the cowl.
The cowl is outside metal trim with vent louvers and windshield wipers sticking through it, below the windshield. Some cabin air filter installations require removal of part or all of the cowl. A common sign is an asymmetrical 2 piece cowl, with a shorter section on the passenger side.
Two types of cabin air filtration media are sold in the aftermarket: single and multiple stage filters. A single stage particulate filter, maybe just paper, is common in original equipment installations.
Single Stage Filters
These one stage filters trap larger airborne dust, the largest soot, and big allergens like pollen.
Premium cabin air filters typically use an electrostatically charged fiber mat to retain airborne particles. While far better than plain paper, these are not HEPA air filters. What particle size do they let through?
Evaluation of car cabin filters begins around the 10 micron size, with particle filtration efficiency falling rapidly in particle sizes smaller than 3 microns. Few sellers list particle efficiency and those that do may say: "The Cabin Air Filter can capture airborne particles that are larger than 3 microns."
Quality products capture particles as small as one micron, but at lower efficiencies, like 30%. Even the best cannot remove dangerous sub-micron particles.
Many standard one stage filter media are limp, without stiff edges to secure the filter firmly in the duct or plenum chamber. This allows dirty air to bypass.
Bypassing is often intentionally engineered to protect downstream AC components from overload.
Multiple Stage Filters
A multi-layer car air filter, typically using some activated carbon, reduces toxic gases and odors. Builders claim tests have shown carbon monoxide levels are reduced with the multi-stage filter models, but I think this is due to restricted intake rather than the actual removal of carbon monoxide.
Multiple stages on quality filters can have progressive size layers like prefilters in room air purifiers. The carbon layer comes last. More stages are definitely better. Best models have strong framing and sealed edges.
A top quality 5 stage charcoal filter may cost $20 to $35, about double the original equipment replacement. This is a very small price for healthier air in the cabin.
Replacement Filter Rip-Offs
Driving conditions will determine the service life of a cabin air filter. Urban pollution and/or rural dust call for frequent changes.
Filter replacement is called for when reduced airflow lowers air conditioner, defroster, and heater throughput, but filters should be exchanged long before this is noticed. Odors from the AC ducts may be a signal. Owners' manuals usually recommend replacement around 15,000 miles.
Can I Do It Myself?
Do-it-yourselfers and shade tree mechanics will have no problem with 99% of cabin air filter installations. A few may require removal of the passenger side wiper assembly.
Installing a cabin filter can be a 20 second job anyone can do, like opening and closing a kitchen drawer. But some can require 30 minutes of a mechanic's time.
While quick-lube operators were slow to catch on, industry journals now report that cabin air filters are their highest margin upsale service. It's a new slant on the old service station low oil scam.
Workers are trained to spot the vehicle models with the easiest to change cabin air filter media. They offer an inferior new filter only to drivers of those car models. The cost is less than dealer service departments, but is excessive for the easy job performed.
It is important to get the correct filter for the application. Slick operators will sometimes substitute incorrectly fitting, cheap, air filter media.
If you are not mechanically inclined, I recommend insisting on premium multi-stage filter media and observing the process to learn how much time it actually takes.
I recommend frequent exchange of original equipment cabin air filters, using 5 stage premium quality aftermarket products.
Whether your car has original equipment cabin air filtration or not, please consider an aftermarket car air purifier.
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