Last week when I turned my A/C on it poured out this smell that burned my nose. It was almost like one of Bohl's bowel movements, but not as severe. With the A/C off and the fans blowing, there's no smell. The second I hit the button, though, the smell runs right back through the vents. My Dad said it could be mold building up on my A/C compressor

but I see nothing (and don't understand how that could logically cause the air to smell) and it wasn't a slowly building smell...it was like a rank fart that hit out of nowhere and won't go away. What could this be?