air vent smell?

hey guys, well on my 92 camaro i noticed when i first start it up when it is cold and i go to turn the heat on for the first 15-20 sec i get this exhaust smell in my vents. Does any one know what can cause this?

Exhaust leak :dunno:

It's been a while since I've thought of it, but the system pulls in fresh air from the cowl vent on the front of the dash.

You sure it's exhaust and not coolant?

ok now i know what it might have been, I just smelled a burning smell last night and i was like what is that? so i went to turn the air vent speed down to low and the switch was SO hot and just burnt up. So now i can't change the vent speed. So now when i turn it on it is on high all the time, i am going to replace it soon. Atleaste it is not stuck on low.