Quote:
Originally Posted by freebeard
I thought it was methane that kills farmers in manure pits.
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While that certainly makes it a heavy topic, it doesn't mean CH4 is more dense than air at typical atmospheric (or tire) pressure and temp..
I haven't even heard of this so I am not well versed in the phenomena, but I suspect a couple things could be at work in those cases.
First, not all the oxygen needs to be displaced to cause unconsciousmess. Unconsciousness is pretty quick with less than 4% O2. One or two breaths. Falling unconscious would of course make death more likely as it brings the face closer to the source of the displacing gas and it removes the best chance for getting clear of the anoxic area.
Second, the manure may be actively emitting methane. Even being less dense, there may be enough especially in a pit to displace oxygen below levels needed for consciousness.
Third, the pit and methane being emitted might be cooler than the surrounding air. It wouldn't have a temperture difference sufficient to make methane more dense than air, but it might offset the difference in density a little.