# Why does the smoke from my chimney go down? **URL:** \ **Category:** Factual Questions\ **Created:** [January 17, 2012, 6:31pm UTC](https://boards.straightdope.com/t/why-does-the-smoke-from-my-chimney-go-down/609811 "2012-01-17T18:31:50Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![shiftless](https://avatars.discourse-cdn.com/v4/letter/s/e9c0ed/32.png) [@shiftless](https://boards.straightdope.com/u/shiftless)\ **Post date:** [January 17, 2012, 6:31pm UTC](https://boards.straightdope.com/t/why-does-the-smoke-from-my-chimney-go-down/609811/1 "2012-01-17T18:31:50Z")
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? ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [January 17, 2012, 7:10pm UTC](https://boards.straightdope.com/t/why-does-the-smoke-from-my-chimney-go-down/609811/2 "2012-01-17T19:10:48Z")
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. ---
**Author:** ![Kiber](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kiber/32/317_2.png) [@Kiber](https://boards.straightdope.com/u/Kiber)\ **Post date:** [January 17, 2012, 7:17pm UTC](https://boards.straightdope.com/t/why-does-the-smoke-from-my-chimney-go-down/609811/3 "2012-01-17T19:17:12Z")
My guess would be a [temperature inversion](http://en.wikipedia.org/wiki/Inversion_(meteorology)). ---
**Author:** ![Galty\_Boy](https://avatars.discourse-cdn.com/v4/letter/g/7c8e57/32.png) [@Galty\_Boy](https://boards.straightdope.com/u/Galty_Boy)\ **Post date:** [January 17, 2012, 8:21pm UTC](https://boards.straightdope.com/t/why-does-the-smoke-from-my-chimney-go-down/609811/4 "2012-01-17T20:21:20Z")
Is your chimney above the roof ridge? if not, wind will roll smoke around on slant of roof.!! Your chimney must be above Roof Ridge. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [January 17, 2012, 8:49pm UTC](https://boards.straightdope.com/t/why-does-the-smoke-from-my-chimney-go-down/609811/5 "2012-01-17T20:49:49Z")
> [@shiftless](#): > > …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.” [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. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [January 17, 2012, 10:29pm UTC](https://boards.straightdope.com/t/why-does-the-smoke-from-my-chimney-go-down/609811/6 "2012-01-17T22:29:43Z")
It’s pretty normal in cold, still conditions in my experience, but I’m not too sure of the mechanism. [This page](http://www.usatoday.com/weather/resources/askjack/wjack3.htm) offers a suggestion, but I’m sure I’ve noticed the same behaviour under high pressure too. > [@](#): > > Q: Why does the smoke from a wood fired chimney sink during low pressure and rise during high pressure? > > A: High pressure is typified by clear skies, dry air, calm winds and cool nights. Cool, dry air near the ground is denser than the warm air leaving the chimney. The chimney smoke will rise until moves into air of equal or lesser density. In advance of a low- pressure system, the air will typically have more water vapor. This water vapor will condense on small particles in the chimney smoke, creating small water droplets that are of equal or greater density than the surrounding air. This smoke will spread horizontally with the prevailing wind without rising much in the air. > > Keep in mind that atmospheric pressure is just one of the variables that play a role in the behavior of chimney smoke. Wind speed and the temperature profile of the atmosphere are also important factors. ---
**Author:** ![tim-n-va](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tim-n-va/32/3001_2.png) [@tim-n-va](https://boards.straightdope.com/u/tim-n-va)\ **Post date:** [January 18, 2012, 9:52am UTC](https://boards.straightdope.com/t/why-does-the-smoke-from-my-chimney-go-down/609811/7 "2012-01-18T09:52:54Z")
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”. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [January 18, 2012, 10:16am UTC](https://boards.straightdope.com/t/why-does-the-smoke-from-my-chimney-go-down/609811/8 "2012-01-18T10:16:52Z")
> [@Gary\_T](#): > > [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. Concur. At worst, something is wrong with The Outdoors. ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [January 18, 2012, 10:50am UTC](https://boards.straightdope.com/t/why-does-the-smoke-from-my-chimney-go-down/609811/9 "2012-01-18T10:50:10Z")
Pour some water in the fireplace and tell us whether it goes up or down. That would help rule out at least one thing. ---
**Author:** ![Icerigger](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/icerigger/32/432_2.png) [@Icerigger](https://boards.straightdope.com/u/Icerigger)\ **Post date:** [January 18, 2012, 12:04pm UTC](https://boards.straightdope.com/t/why-does-the-smoke-from-my-chimney-go-down/609811/10 "2012-01-18T12:04:21Z")
Are you using a different kind of wood? In our fireplace a combination of green wood and wind direction can sometimes make the smoke “back up” a bit. ---
**Author:** ![shiftless](https://avatars.discourse-cdn.com/v4/letter/s/e9c0ed/32.png) [@shiftless](https://boards.straightdope.com/u/shiftless)\ **Post date:** [January 18, 2012, 1:52pm UTC](https://boards.straightdope.com/t/why-does-the-smoke-from-my-chimney-go-down/609811/11 "2012-01-18T13:52:54Z")
> [@Mangetout](#): > > Concur. At worst, something is wrong with The Outdoors. 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! ---
**Author:** ![Doug\_K](https://avatars.discourse-cdn.com/v4/letter/d/b5ac83/32.png) [@Doug\_K](https://boards.straightdope.com/u/Doug_K)\ **Post date:** [January 18, 2012, 3:31pm UTC](https://boards.straightdope.com/t/why-does-the-smoke-from-my-chimney-go-down/609811/12 "2012-01-18T15:31:39Z")
> [@Cosmic Relief](#): > > Pour some water in the fireplace and tell us whether it goes up or down. That would help rule out at least one thing. Maybe he bought his house from Mrs. Piggle-Wiggle. ---
**Author:** ![jasg](https://avatars.discourse-cdn.com/v4/letter/j/f0a364/32.png) [@jasg](https://boards.straightdope.com/u/jasg)\ **Post date:** [January 18, 2012, 10:29pm UTC](https://boards.straightdope.com/t/why-does-the-smoke-from-my-chimney-go-down/609811/13 "2012-01-18T22:29:43Z")
Given the recent holiday season, have you [cleaned](http://peelslowlynsee.files.wordpress.com/2010/03/gahan-wilson-0ct-1964-miss-emmy.jpg) it lately? ---
**Author:** ![VOW](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/vow/32/3043_2.png) [@VOW](https://boards.straightdope.com/u/VOW)\ **Post date:** [January 19, 2012, 3:41am UTC](https://boards.straightdope.com/t/why-does-the-smoke-from-my-chimney-go-down/609811/14 "2012-01-19T03:41:39Z")
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