Hyundai Repair: smell coming from air conditioner, silicone caulk, hydrogen sulfide

Question
When I cold start my 2004 Santa Fe, I get a noxious odor coming through my vents.  It smells like alot of silicone caulk in a closed room.  Any ideas on what it could be?

Answer
If it's originating from the ventilation system, it could be something growing in the moisture that frequently resides there.  If this is the case, I'd recommend spraying air freshener into system.  To do this, turn the temperature to full hot and the fan to full speed, turn on the a/c, and select fresh air.  Then spray the air freshener into the holes in the plastic cowling at the bottom of the outside of the windshield on the passenger side.

If the odor is originating from outside the vehicle, it's possible you have excessive hydrogen sulfide in your exhaust.  If this is the case, you might try switching brands of gasoline.  Different gasolines have different sulfur contents.