Tricky and nasty indeed. I know people who have had close calls. If I had been in that vehicle, a window would have been cracked, period. Not just for fresh air, but to vent excess moisture.

At the time I didn't have suitable measuring equipment, but now I have an industrial client where portable gas monitoring (including CO) is routine, including pumps and tubing for remote sampling. Maybe I could pull a favour. Hmm.