Only when you vaccum? Erm, is your vacum cleaner kicking up the steanch? The vacuum I use needs to be cleaned after every used (cause of our pets) or it shoots out a smell like no other. Though it is some complicated water based cleaning system; so I am not sure the problem would be the same. I think the last time lyle and I made it half way through vacuuming, it smelled like tuna fish and broken dreams. It works that well XD

I have also used some special carpet powder I buy at wal-mart. It makes my carpet smell like roses. JUST LIKE I LIKE IT!