Cabin Air Filters

Breathing easy inside your car
The crisp smell of early fall, the metallic twinge of mountain rain, the organic whiff of freshly turned farmland-all part of those bucolic family vacation trips of our youth. But, fast forward to the era of metropolitan areas that have gobbled up real estate faster than The Donald, then add the knowledge that our perpetually runny nose could be the result of complex allergies. Now those smells wafting into the family sedan may not be so welcome.
In the year 2000, roughly 40 percent of all new vehicles offered cabin air filters as standard equipment, or as an option as part of the heating, ventilation, air conditioning (HVAC) system. That figure went up to 80 percent by 2005, even though some automotive manufacturers started including them in the 1980s. Approximately 30 million vehicles in North America now have the ability to shut out the odors of diesels or urban smog as well as pollen and other airborne contaminants by way of the HVAC system. So, we must be breathing easy, right?
Just like the air filter that feeds your engine, the cabin filter can become clogged with gunk. Too much buildup and these contaminants become concentrated in the vehicle passenger compartment. Eventually, the ventilation system suffers, first with reduced efficiency, then by mechanical problems from the effort of pulling air through the clogged filter.
Again, like your engine's air filter, this cabin air filter has to be replaced, at least annually, or more if you drive in smog-shrouded urban areas or suffer from allergies. Engineers who have studied cabin air filters figure that if the unit is not changed regularly, the air in your passenger compartment is six times fouler than strolling down a Los Angeles freeway interchange. An early clue that your filter is clogged is a pervasive musty smell when the system is on (either for venting in outside air, heating or the A/C).
The Process
Many cabin air filters are three layers of filtering material designed to first capture larger contaminants, then smaller ones. In the world of contaminants, small is defined as less than 2.5 microns. To put that in perspective, a human hair is roughly 50 microns thick and one cubic foot of air includes 10 to 80 billion particles. The third layer is made up of activated charcoal to absorb gases and odors. This category of contaminants can cause problems like headaches, nausea and allergic reactions. Cabin air filters look a lot like your engine's air filter but are more flexible since they, generally, have to be coaxed into tight housings. Which brings us to the next point: does your vehicle have a cabin air filter and, if so, where is it?
The best way to figure out if your vehicle has the filter is to check the owner's manual. Unfortunately, this particular filter may have crept under your mechanic's radar and not been included in your regular service. While your manual will tell you if you have one, in most cases it fails to tell you how to change it yourself. At best, it may indicate with a vague arrow just where the filter is.
Clear the Air
Companies such as Wix Filters, the manufacturer that makes many OE filters as well as replacements, have made an effort to provide more detailed instructions. In some vehicles, the filter is under the hood; some models require simple hand tools. Others can be popped out with no tools at all to remove plastic covers on the cowl. Some vehicles house the filter under the dash, just above the front-passenger footwell and beneath the HVAC module.
If your vehicle pre-dates the inclusion of cabin air filters, there's really no way to retrofit the system to accommodate one. However, if you have a late-model vehicle that offered the cabin air filter as an option, but your specific vehicles doesn't have one, that means there's a place to put it. All you have to do is find out what filter will work and have it installed. Fortunately, automotive service businesses are becoming more aware of the value of the cabin air filter and the necessity to replace it regularly. So, check your owner's manual, have a talk with your mechanic and start breathing easier.

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