Cold weather here lately so we built a fire in our wood stove. When I look out the front window, the smoke is rolling down the slope of the roof and our whole neighborhood has a smokey/foggy look. My wife says “there’s something wrong with our chimney, we should get it looked at.” I say it has to do with the weather (in some way I don’t understand.)
Temps around 32F, very light winds, moderate pressure.
The whole weekend, every time I looked , the smoke was drifting downward. It’s hot air, shouldn’t it go up?
if the air is very cold it can cool the smoke very rapidly as it leaves the chimney and the particles will then sink rather than rise. also air blowing can force a smoke stream in its direction.
in your cause the air may be very dense with moisture also and forcing the smoke down.
[To your wife:] If the smoke is not filling the room inside, and goes up the chimney before it goes down along the roof as described, then the chimney has to be working. How could the smoke get to the roof if the chimney wasn’t working?
When the smoke comes down the chimney itself, then there may be something wrong with the chimney.
It’s pretty normal in cold, still conditions in my experience, but I’m not too sure of the mechanism. This page offers a suggestion, but I’m sure I’ve noticed the same behaviour under high pressure too.
My mom (born 1919, limited formal education of about 8 years) used to say that when the smoke went to the ground it was a sign of “falling weather”, i.e. rain, snow, sleet, etc.
The low pressure, high humidity explanations tend to support her southern Appalachia “theory”.
Damned Outdoors. I keep fixing it and it keeps breaking.
Colophon’s link probably explains it in a way I can sort of understand. The pressure at the time was moderate (I looked it up) but rain was moving in, which would be “In advance of a low- pressure system” I think. With this new knowledge I can predict the weather!
Temperature inversion, common under the weather conditions you’ve described. The air, even though clear, is in layers. The smoke cannot penetrate into the uppermost layer, so it “bounces” down and then dissipates. Throw in several chimneys, and you’ll get that haze near the ground.
If it warms up enough, the inversion will disappear.
~VOW