I heard this anecdote from a guy at Fire in the Valley.
This is about another friend who will I won’t name here. On a day when there is absolutely no wind he has propane in a crevasse, the bottom of a little valley and lit it. Since propane is heavier than air, it kind of flows down the river and then he lights it. It doesn’t explode, instead it burns at the interface between the propane and the air. And it’s awesome.