Check elevations at Yellowstone.. I've got one of the Coleman catalytic heaters similar in design to the Buddy heaters.. They will no fire up above 8000ft.. Not enough oxygen... A side effect of this is that when carbon monoxide starts to build up and oxygen level start going down the heater will shut itself off.. However, I have no idea if the propane keeps on flowing when the heater goes out.. Kinda thinking that could be as bad, if not worse than a carbon monoxide overload..
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Rob Duncan
Memphis, TN