Dusty smell coming from vents?

A bit of background, my mom picked this 2014 CX-5 up about 5 months ago with 31,000km on it. She noticed that it had a very stuffy, dusty smell coming from the vents(the type of smell when you're following a car closely on a gravel road, spitting up dust). She took it to the dealer and they replaced the cabin air filter(it was BAD, it had never been changed before and had tree leaves, dirt, silt, pine needles etc. in it and was caked full of crap). She said the smell didn't go away, it just went down in severity, but says it's more or less, back again. Should I check the filter again, maybe not all the crap was collected? If so, where is the cabin filter on these cars?

The cabin air filter is behind the glove box and is easily replaceable. It probably would not hurt to change it again, you can get them on Amazon for $9-$18. Search replacing cabin air filter on here and you will find directions. When I bought by used 2014 CX-5 GT 2 months ago there was a faint cigarette smoke smell. I used a Meguiar's Re-Fresher and it completely eliminated the smell. This might help with the dusty smell. Amazon has them, but I got mine at Walmart. (Don't let the dealership change that filter again, you can do it for your Mom and save her $50-$75!)

Here is the video on how to change cabin air filter.

Also be sure to lift the hood and clean up all the leaves and debris from where the cabin gets it's air, which is where the windshield and hood meet. Lots of leaves can get trapped in there.

This other thread showed some other places for leaves to hide...
http://www.mazdas247.com/forum/showthread.php?123853746-Concerning-Build-up-of-Leaves-in-Wheel-Well

Okay thanks! Yeah they charged her $86 to replace it!! Might as well have gotten an oil change done for that price!