If it's mold related, you can use a product called BG Frigi-Fresh. The BG products are considered the best but they are expensive and hard to find. The dealer may carry this too. If you suspect carbon monoxide, you can visit a local general aviation airport and see if they have the carbon monoxide testers. These are fairly cheap, maybe 3 or 4 dollars. The card will change colors if carbon monoxide is present. With that said, my S70 also had a strange air conditioner smell right before the evaporator failed. This was a $2000 repair at the the dealer because the whole dash has to be removed to fix it.