Originally Posted by
JayUtah
Right, buoyancy. Smoke does not rise. Smoke is a solid aerosol entrained in a column of heated air. In a perfectly quiescent environment, smoke will fall to the ground just as effectively as dust, or a handful of marbles.
And it will fall quite nicely when entrained with cool air. I’ve observed this while we were poking ceiling tiles out in a grocery store that had a fire on the roof. Some of the smoke got into the cool air of the false ceiling space, and drifted down when we opened the ceiling checking for extension.
That was because the smoke was in air that was
denser than the ambient air mass. It had nothing to do with an atmospheric pressure gradient.