GenVibe - Community for Pontiac Vibe Enthusiasts

I have a 09 AWD & if I have the blower on (no AC or heat) you get this web dog smell from the vents. I can't smell it if the AC or Heat is on but my Wife said she can.I have changed the cabin filter and engine filter but still smell it.. Nothing is sitting on the vents from were the windshield meets the hood like leafs etc. Ideas?

I sometimes get this too. Most of the time I notice it will happen if there is a drastic change in outside temperature, or if it's raining/been raining. It'll also happen a lot, if I switch the temp from cold to warm; AC or no AC.