I thought the bulk of our major smoky days was gone until I drove in from Christina Lake this past weekend. It’s back. You may be thinking all this smoke will take its toll on your engine’s air filter and it might be a good idea to get it changed. In reality smoke particles are smaller than what the typical engine air filter was designed to trap.
There is a filter in roughly 60 per cent of the vehicles on the road (90 per cent of newer vehicles) that is probably ready for a change after this smoky summer season. You may or may not have ever heard about it. It is the cabin air filter.
Cabin air filters filter all the air entering your vehicle through your HVAC system (Heating, Ventilation, and Air Conditioning). The air that flows into your vehicle is usually let through a grille type area at the bottom of your windshield. From there it is collected and ducted over to your heater fan. On the way to the heater fan the air will flow through an air filter that will remove all kinds of nasties depending on the design and quality of the filter. The location of this filter may not be very obvious. You can usually find where it is and how to replace it in your owner’s manual.
Cabin air filters are basically of two varieties, dust filters or dust and odor filters. The dust filters will remove 100 per cent of all particles greater than 3 microns in diameter (17 to 181 microns is the diameter of a human hair.) They typically remove 95 to 99 per cent of particles between 1 and 3 microns. They will also trap a percentage of particles down to .3 microns. At this size we are talking about pollen, bacteria, mold spores, exhaust soot and the dreaded smoke. Not perfect filtration but close.
Dust and odor filters usually add a layer of activated charcoal or baking soda. Thus they absorb odors and air pollutants.
Since these filters trap very small particles they can plug up very quickly in a dusty environment. The typical recommended replacement interval is between 25 000 and 50 000 kilometres. A plugging filter will seriously reduce the air flow that your vents can provide to the driver and passengers.
Customer complaints that may indicate a clogged filter run the gamut from poor heating to poor cooling to a noisy fan.
The cabin air filter is also one of those items that the local critters like to source for building material. We frequently find filters that are no longer filtering because some rodent has chewed right through the filter. Another good reason to check the filter even if the air flow seems good.
Replacement filters can be the dust variety or the dust and odor type. Many vehicles have an available upgrade. Some vehicles may not even come with a filter but they have a place for one.
It can be your choice to put one in. I recommend putting one in if you can. It stops a lot of junk from getting into your ducting. Leaves and various debris are kept away from the fan, air conditioning evaporator, and heater core. When that kind of debris gets stuck in heater cores and evaporators it can create molds and acids that ruin those expensive to replace parts. So generally a cabin air filter will be your friend unless it is always being used as building material for your pet varmint.
Trail’s Ron Nutini is a licensed automotive technician and graduate of mechanical engineering from UBC. E-mail: firstname.lastname@example.org