by Kara Bishop
VehicleMD Staff Writer
Originally published in Fall 2011 Issue

Does your car’s interior smell funny? Do you buy air fresheners by the dozens, but the odd smell is only masked for a brief while and then comes back? Identifying the real problem behind the mysterious odor can be difficult; especially if there are parts on your car that you weren’t aware existed—like the cabin air filter.

According to experts from allergybegone.com, many car owners don’t realize that such a part exists in their vehicles, much less if it ever needs to be changed.

Whether you know about it or not, a cabin air filter is an essential part of your car’s ventilation system—removing pollutants, solid contaminants like dust and soot, and absorbing odors and gases—that needs to be maintained like the rest of a vehicle’s components. Cabin air filters may also be known as passenger compartment filters, interior ventilation filters, pollen filters or dust filters.

Cabin Air Filter Facts:

Most Cabin air filter replacement services take less than 15 minutes.

The cabin air filter protects car passengers from pollen, spores, bacteria and other airborne contaminants. In addition, carbon cabin air filters are impregnated with activated charcoal to prevent outside odors from entering the car's passenger compartment.

The cabin air filter aids in the operation of a vehicle's heating and air conditioning systems by keeping them free from contaminants.

Most automakers recommend that the cabin air filter be changed every 12,000 to 15,000 miles or once a year.

Contaminants inside a vehicle can be as much as six times higher than the levels outside the vehicle.

Cabin air filters are located under the vehicle's hood, behind the glove box or under the dash.

There are two different types of filters: carbon (often referred to as charcoal-activated cabin filters) and paper (particle).

These filters may look similar in construction to the standard engine air filters, but some unique characteristics make them different. The original filter is the particle filter, which is constructed with two layers of material: a polyester base layer woven to trap larger dust particles, and an electrostatic-charged layer which acts as a magnet to draw the finest dust particles out of the air.

Innovative technology has given us the carbon filter, which not only keeps irritating particles from entering the cabin of your car, but also includes a layer of activated carbon, or charcoal, which absorbs unpleasant odors and gaseous compounds.

Cabin air filters came along in the mid-1980s when air pollution became a problem. Today more than 80 percent of all new import or domestic vehicles have a cabin air filter, while 40 percent of vehicles actually on the road contain cabin air filters.

Over time, the air filter in your car becomes less efficient as it gets dirty with use. This can be the cause of the strange odor you smell (and are trying to get rid of with dozens of 99-cent air fresheners). However, it’s not just the smell that will affect you, because a dirty air filter can decrease the performance of the air conditioning and heating systems—causing an even more uncomfortable ride.

Vehicle manufacturers usually recommend replacing the filter at least once a year or every 12,000 to 15,000 miles (even more if you’re driving in areas with heavy smog or dusty conditions), and the service interval can depend on the type of filter being replaced—carbon or paper—and the cabin’s filter exposure to the environment as well as the amount of miles on the vehicle.

Experts say to change the filter as often as necessary to prevent the filter from clogging—or in the case of cabin air filters that also absorb odors, as often as needed to keep unpleasant odors to a minimum. Under “normal” driving conditions for a vehicle driven primarily in a city or suburban area, the average service life of a typical cabin air filter is about a year. For a vehicle in a rural area that is driven frequently on unpaved roads, the service life of the filter may only be six months or less. It all depends on the vehicle and the driving condition the vehicle falls under.

So, why change these filters? Obviously to ensure the quality of air that passengers breathe every minute they are in the car—this is especially important for people with allergies and respiratory problems. Also, the interior of the car remains cleaner with properly filtered air, and a dirty filter puts more wear on the ventilation system; since there is higher air-flow resistance, the blower must work much harder. This process will eventually reduce the heating and air conditioning performance.

No matter what, it’s important to remember that the cabin air filter needs to be maintained. If you can’t figure out what that smell in your car is—we are all guilty of leaving the gym shoes in the car on a hot day—or your heating and air conditioning is not working like it should, then take the vehicle to your service center and have the filter professionally inspected and replaced, if necessary.

 

A/C Odor Service

If the cabin air filter is not the source of your odor dilemma, there are other possible causes. If the air coming our of the vents smells musty, it is possible mold or mildew is growing inside your A/C system's evaporator. Fortunately, many auto service facilities offer an A/C odor service that can remove those offending smells. This service generally uses a chemical foaming agent to remove mold and mildew from the air conditioner. If your A/C isn't smelly, keep it that way by following these tips: Musty odors are often started by going in a drive-through carwash tunnel with your air conditioner set on "intake from the outside." Either turn your A/C off or put it on the "recirculate" setting. If you don't, you're allowing water to be splashed in through the vents around the windshield wiper area, which can cause mildew and mold. Running your air conditioner on its maximum setting most of the time can leave odor-causing moisture inside the system. Instead, choose a lower setting more often. On a particularly hot day, when you have to use the maximum setting, change it to a lower setting shortly before turning the car off. This will give your air conditioner a chance to dry out and prevent mold from forming. Another quick fix includes a disinfectant spray. Spray the disinfectant directly into the vents around the windshield area on the outside of your car. Run the air conditioner on "outside air" for the first several miles and then switch to "recirculate." This inside airflow is stronger and flushes the disinfectant through the system. It is important to note that these suggestions are only temporary/preventative solutions. If the odor problem persists, visit your local lube shop for an inspection.