Fresh air blower - smells like a skunk

[ejp]

Last night was the first cool night since I've owned my 88 Carrera. The windows were closed and I decided that I would try my luck at deciphering the HVAC controllers. Assuming that the two topmost sliders are for fresh air (up/down and fan speed), I slid them to the right and my car quickly smelled like a skunk. I switched the system off, rolled the windows down to clear the car out, and tried again. More skunk.

I figure that there must be a modest bacterial and/or fungal colony living in there. Is there an easy solution to this? Our host sells "Einszett A/C Odor & Bacteria Remover (Klima-Cleaner)", which comes with some dire warnings having to do with hazardous materials, certified mechanics and professional application only.

The site also indicates that this is for AC...is this the correct product to use through my fresh air system? Anyone have experience with this stuff? How would I use this for my application? My first thought to remove the fresh air grill in front of the windshield, insert hose and spray with the system on full.

Thanks,
-Ethan