My wife is reading a book wherein the entire plot basically revolves around the notion that a car’s tail pipe buried in snow caused the occupants to die of carbon monoxide poisoning (leading to a suspected murder plot).
I found this hard to swallow, but googling turned up a couple of possible supporting cites.
Anecdote: I once backed into a mud bank, plugging up my tailpipe. My car died pretty much immediately and wouldn’t re-start until it was cleared. Also, I presume exhaust is hot enough to melt fresh fallen snow. (in the book, it was fresh fallen - not packed snow. There was enough snow that it required an hour (!) of shoveling [so why have your wife wait in a running car for an hour? but I digress]).
So if it was plugged enough for it to push exhaust back into the cab, why wouldn’t an engine just quit (ala Beverly Hills Cop 1984)?
Or conversely, If the exhaust melted enough snow, wouldn’t it just dissipate into the snow?
The exhaust would melt snow which would run down and melt more snow underneath, possibly creating a hollow in the snow that redirects exhaust under the car which had an open fresh air vent or some other air leak. There also could be a leak in the exhaust system made worse by back pressure on the tail pipe, or a leak that just wasn’t noticed before which has led to many deaths in real life by carbon monoxide over the years.
In the good old days when rust prevention was less of a automaker priority, holes in the floorboars were not unknown. (Friend of mine mentioned being pulled over by the Mounties one evening. They searched the car but found no open beer, but when they drove away afterwards there were several beer bottles sitting on the road…)
The risk of leaky mufflers, leaking floor pans, etc. was always mentioned back then.
I don’t have any personal anecdotes, but this is one of the cautions that we get when learning to drive in Saskatchewan. If your car slips into a ditch with snow, and you’re staying in it, waiting for help, make sure to clear the area around the tailpipe so there’s no chance of carbon monoxide buildup.
I understand that the amount of carbon monoxide produced by modern cars is lower than it used to be, so perhaps not so much of an issue?
The three-way catalyst and closed-loop fuel injection in modern gasoline-engine cars does a pretty good job reducing engine-out levels of CO. Once an engine and its exhaust aftertreatment system is fully warmed up, tailpipe-out CO concentrations are on the order of 2000 ppm. However, assuming no dilution with ambient air, this is still enough to kill a person after maybe an hour of exposure: