But it sounds like it's hard to get a handle on how common it is. It feels like it's more on the level of "a handful a year in North America/freak occurrance", rather than "common way to die".
Right, but in particularly heavy snowfall, it's not hard to imagine snow encasing the chassis. Once the snow forms a barrier around the body, the exhaust has nowhere to go. Or if the pipe gets blocked (which is a bit harder to imagine, since there's heat coming out of there), and there are exhaust leaks, the exhaust is directed up through the chassis. It doesn't have to be a perfect seal to raise the CO level!
I was recently stuck in a 3 hour backup in sub-freezing temps in moderate snowfall, and it was nice to be able to leave the engine running for heat. In the winter, we have a contingency where it's possible to be stuck in your vehicle overnight in heavy snowfall, and my plan was always to wake up every couple of hours to ensure the snow was clear of the car.
https://www.cdc.gov/mmwr/preview/mmwrhtml/00039929.htm https://www.rearviewsafety.com/safety/news/news-release-dead...
But it sounds like it's hard to get a handle on how common it is. It feels like it's more on the level of "a handful a year in North America/freak occurrance", rather than "common way to die".