strange smell coming from vents

i have a strange smell coming from the air vents in my 1978 lesabre. i ran out of gas so i had a friend drive me to get some, and upon starting the car there was this smell. i checked the hood, no smell the there. it runs perfect, actually its running better than ever. normally it idles a little rough, but right now its perfect. the smell is something like burning latex, or maybe rubber. something burning. please help :confused: