The cabin filter is a paper or textile filter medium, fitted to strain out airborne contaminants before they enter the cabin. Most cabin air filters are strictly filtration mediums, but some feature odor-eliminating properties.Basic cabin filters, or particulate cabin air filters, depending on the brand, can filter out up to 99% of contaminants over 3 µm in size, including PM10, dust, ash, pollen, spores, hair, feathers, leaves, and insects. Some filters can filter out over 95% of particles between 1 µm and 3 µm in size, such as bacteria, some viruses, finer dust and soot, and dangerous PM2.5, produced by vehicles of every size. Aside from allergic reactions, which can impair the driver, some contaminants are known to cause serious health problems. The World Health Organization (WHO) has linked PM10 and PM2.5 (particulate matter less than 10 µm or 2.5 µm) to increased incidence of asthma, lung cancer, respiratory disease, cardiovascular disease, to name a few.

There are several factors that can affect the lifespan of an individual cabin filter.
Mileage: Generally, the more a car is driven, the more air a cabin air filter will process, so mileage can be a pretty good indicator of when to replace it.
Time: Somewhat less important is how long the filter has been in service. Particulate filters don´t degrade over time, but carbon filters continue to absorb odors from the moment they are unsealed.
Area: Some areas are dustier than others, and other areas have higher pollen counts. The more contaminants there are in the air, the less time the cabin filter will last.
Season: Many airborne contaminants are greater at certain times of the year. Dust, mold, and pollen levels vary throughout the year.The best way to determine when to replace the cabin air filter is either by visual inspection, olfactory inspection, or by noting how much airflow is being impacted. Fortunately, most modern cabin air filters are easily-accessible, so a five-minute inspection should give you a good idea of filter lifespan.

Replace the filter if it´s filled up, smells bad, or is restricting airflow.

1. To replace the cabin air filter, simply remove the glove box, kick panel, or cowl cover.
2. Then, remove the cabin filter cover, usually held in place by tabs or screws.
3. Slide out the old cabin air filter. You can use a vacuum to prevent captured particles, insects, or leaves from getting through the rest of the system.
4. Install the new cabin air filter, noting correct airflow direction, usually indicated by an arrow. Most flow to the rear of the vehicle or down toward the floor.
5. Install the cabin filter cover, then the glove box, kick panel, or cowl cover.

After replacing the cabin filter, enjoy a few more months of driving in clean air, even when the outside air isn´t.