Changing the cabin air filter in your Mazda 3 can vastly improve the interior air quality when you are running the heat or air conditioning. The cabin air filters often get clogged with leaves, or dirt and debris from the road and can be quite expensive to change if you take it to the dealer. Cabin air filters are available at any parts-store and changing them, even for a novice, should not take very much of your time.
Remove the plastic trim piece under the glove box, near where your left leg would be if you were sitting in the passenger seat. It isn't the floor piece, but the piece directly above it. There are two easy-release clips that allow you to just pull it right off.
Pry the centre console piece (next to the one you just removed) out by prying from the side closest to the shifter until the clips release.
Remove the two screws from the air filter bracket.
Remove the two air filters from the brackets by sliding them out. Remove the bottom one first.
Replace with two new filters.
Screw the brackets back into place.
Replace the centre console piece by lining it up and pushing it into place until you hear it snap together.
Replace the plastic trim piece under the glove box by lining it up and applying gentle pressure until you hear or feel it snap into place.