The air filter is like the nose of your car.  It filters the air that the engine needs to burn the gas.  When the filter gets dirty or clogged up it makes the engine work harder and starts to reduce your fuel economy.  I refer to a dirty air filter like us having a stuffed up nose in the winter time :)

This is something that most shops will check every time you take it in for an oil change but it shouldn’t require changing every time unless you aren’t being diligent with your oil changes.  A general guideline is every 20-24,000 kms.  The exception to this would be if you live on a dirt road or are driving through construction on a consistent basis.

When Mount St. Helens blew it’s top all of the police officers went to the auto parts store and bought all of the filters as they were getting clogged up within a couple of hours from all of the ash falling out the air.  Another person told me they weren’t allowed to drive over 15 miles an hour so that they didn’t stir up all of the ash and put it back in the air.