A cabin air filter cleans the outside air before it comes into the passenger compartment. It filters out common air particles like dust, pollen, spores, bacteria, pollutants, exhaust gas, odors and even sparrows. These high tech filters can block particles larger than 3 microns. By contrast, a grain of sand is about 200 microns. Not all vehicles have cabin air filters because they are fairly new on the scene. About forty percent of new vehicles sold come with cabin air filters, but the number is growing every year. Cabin air filters can make for a very nice driving environment. Your car can be a haven during allergy season with very little dust and pollen getting into the cabin. However, the filter eventually gets clogged. When this happens, your heating and air conditioning flow can become restricted. The filter can even get kind of smelly. Check your owner’s manual for recommended replacement intervals. Often, the owner’s manual forgets about the cabin air filter, so ask your service technician for a recommendation. It’s usually every year or 12,000 miles. Change it sooner if you drive in dusty conditions, or if you start to notice an odor from your ventilation system. So keep your cabin air filter clean. It will make your driving experience much more enjoyable.