Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP
vents intake generally come from the upper shroud. you should smell it from the outside too.
does it smell like a dead animal possibly?
I pull dead rats and mice out of air boxes a couple of times a year.
They will always get stuck in the area around the cabin air filter.
IF you can access it easily, id recommend popping the cabin filter out and look for signs of the filter being chewed.
ITs definatley a good start to your smell.
I hope this info helps,
let me know what you find