I have used "Ozium" for the same problem on various cars. What has worked for me is to turn the car on, open all of the windows and sunroof, turn on the blower, open all vents, then spray a few good blasts of "Ozium" into the fresh air intake below the windshield. Do this a few times and let the fan run a few minutes. Let it air out for a bit and everything should be OK. It may take a few treatments to make it disappear completely. You may also want to investigate changing the dust/pollen filters. Good luck!