In order to improve the air quality in your vehicle it is recommended that you change the cabin air filter every 15,000 miles (this is a generic figure, so consult your manual). If you are on very dusty roads or in the country is better to change it very regularly so that you do not let harmful particles into the cab of your vehicle. It is also recommended that you change are regularly if you have pets riding in your vehicle.
A cabin air filter may be in the outside air intake, visible with the hood up and perhaps a cover lifted. Or it will be under the dash in one or both of two general locations:
Most of the time is located underneath the dash, encased in a plastic box. What you need to do is remove a couple of the clips that hold it in place and the filter slides right out. This is normally an easy process to do when you’re trying to maintain your vehicle. Make sure that you remove the filter, as well as any debris that may be in the cabin air filter box. You want to use a vacuum to suck out anything that could be left in the box before you install the new filter.
The cabin filter is a type of air filter that in some respects—such as pleating to provide a lot of surface area in a small package—may resemble an engine air filter. However, it usually is made of different materials, the main one being a charcoal layer in many elements. Like some engine air filters, the dust and pollen filtering element is electrostatically charged, which means it's made with fiber particles that have been given either a positive or negative static electrical charge. Airborne particles are negatively or positively charged, so they are attracted to the opposite-charge fibers.
Tired of paying $16 to $25 for a new cabin filter for your Toyota. Well here is a quick inexpensive mod.
I was rather disappointed with the performance of the Toyota cabin filter on my 4th Gen 4Runner, after driving a BMW the filter on the Toyota felt like it only blocked leaves. As I go offroad quite a bit and most of the roads are dusty, I found that a lot of dust actually passed through the stock filter. The stock filter also didnt last more than 5000 miles. So after hearing some Lexus owners actually use house A/C filters I decided to give it a try.
I use these 3M filters in my house and have been very impressed by their performance. They are about $16 at Home Depot for a 20x30. Which allows you to cut about 4 replacement cabin filters out of one. See stock filter on big 3M filter.