# Why Doesn't Soot Burn? **URL:** \ **Category:** Factual Questions\ **Created:** [May 13, 2005, 2:53am UTC](https://boards.straightdope.com/t/why-doesnt-soot-burn/303634 "2005-05-13T02:53:45Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![Jim\_B](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jim_b/32/4338_2.png) [@Jim\_B](https://boards.straightdope.com/u/Jim_B)\ **Post date:** [May 13, 2005, 2:53am UTC](https://boards.straightdope.com/t/why-doesnt-soot-burn/303634/1 "2005-05-13T02:53:45Z")
Charcoal burns because the carbon in it acts as a fuel. But soot (and by soot I mean the black part of **any** burned substance) doesn’t apparently. Why doesn’t it and exactly what makes soot so chemically different from charcoal in this way (after all, they both are black and they both are mostly carbon)? ---
**Author:** ![Padeye](https://avatars.discourse-cdn.com/v4/letter/p/a9a28c/32.png) [@Padeye](https://boards.straightdope.com/u/Padeye)\ **Post date:** [May 13, 2005, 3:11am UTC](https://boards.straightdope.com/t/why-doesnt-soot-burn/303634/2 "2005-05-13T03:11:34Z")
Soot is is carbon that is already burned. Charcoal may look burned but it is made by heating wood while depriving it of oxygen. This drives off all the stuff that keeps the carbon from burning efficiently like water and other compounds found in wood. ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [May 13, 2005, 3:25am UTC](https://boards.straightdope.com/t/why-doesnt-soot-burn/303634/3 "2005-05-13T03:25:17Z")
> [@Padeye](#): > > Soot is is carbon that is already burned. More correctly, soot is carbon that has burned incompletely. With adequate heat and oxygen, no soot will be formed. Soot is residual carbon that remains after incomplete combustion. ---
**Author:** ![Shalmanese](https://avatars.discourse-cdn.com/v4/letter/s/45deac/32.png) [@Shalmanese](https://boards.straightdope.com/u/Shalmanese)\ **Post date:** [May 13, 2005, 4:08am UTC](https://boards.straightdope.com/t/why-doesnt-soot-burn/303634/4 "2005-05-13T04:08:34Z")
But if soot is just carbon, why won’t it burn? presumably, theres enough oxygen and presumably, the C-C bonds in soot aren’t as strong as the C-O bonds in carbon, otherwise, nothing would burn. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [May 13, 2005, 5:03am UTC](https://boards.straightdope.com/t/why-doesnt-soot-burn/303634/5 "2005-05-13T05:03:24Z")
> [@Shalmanese](#): > > But if soot is just carbon, why won’t it burn? presumably, theres enough oxygen and presumably, the C-C bonds in soot aren’t as strong as the C-O bonds in carbon, otherwise, nothing would burn. I think that is the point that **fear itself** was making. During the combustion there was insufficient oxygen to burn the fuel completely. By the time the unburned carbon, the soot, forms as particles in the air there is plenty of oxygen but by then the temperature has fallen below the kindling temperature. ---
**Author:** ![Rayne\_Man](https://avatars.discourse-cdn.com/v4/letter/r/df705f/32.png) [@Rayne\_Man](https://boards.straightdope.com/u/Rayne_Man)\ **Post date:** [May 13, 2005, 6:18am UTC](https://boards.straightdope.com/t/why-doesnt-soot-burn/303634/6 "2005-05-13T06:18:22Z")
Soot does burn. Have you ever seen a chimney fire? Once it gets going it can be fierce. What you see burning is the soot which has built up , helped by the abundance of oxygen in the air rushing up the chimney. This is why it is important that chimneys are swept regularly. In France you cannot get house insurance until you have produced a certificate to show that your chimney has been swept on a regular basis. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [May 13, 2005, 6:31am UTC](https://boards.straightdope.com/t/why-doesnt-soot-burn/303634/7 "2005-05-13T06:31:41Z")
> [@Rayne Man](#): > > Soot does burn. Have you ever seen a chimney fire? Once it gets going it can be fierce. What you see burning is the soot which has built up , helped by the abundance of oxygen in the air rushing up the chimney. This is why it is important that chimneys are swept regularly. In France you cannot get house insurance until you have produced a certificate to show that your chimney has been swept on a regular basis. I always thought that chimney fires were the result of resins, etc. from the wood[condensing on the cool chimney walls.](http://www.csia.org/homeowners/chimfire.htm) ---
**Author:** ![Rayne\_Man](https://avatars.discourse-cdn.com/v4/letter/r/df705f/32.png) [@Rayne\_Man](https://boards.straightdope.com/u/Rayne_Man)\ **Post date:** [May 13, 2005, 7:00am UTC](https://boards.straightdope.com/t/why-doesnt-soot-burn/303634/8 "2005-05-13T07:00:46Z")
I am talking about coal fires. There you do get a lot of soot produced , some of which ends up in the chimney. ---
**Author:** ![Rayne\_Man](https://avatars.discourse-cdn.com/v4/letter/r/df705f/32.png) [@Rayne\_Man](https://boards.straightdope.com/u/Rayne_Man)\ **Post date:** [May 13, 2005, 7:09am UTC](https://boards.straightdope.com/t/why-doesnt-soot-burn/303634/9 "2005-05-13T07:09:02Z")
Here is an extract from a web-site on chimney linings and fires :- \*Soot Build Up Soot and condensate deposits form on the inner wall of the flue liner. These deposits can re-ignite and cause a chimney fire.\* ---
**Author:** ![Sigene](https://avatars.discourse-cdn.com/v4/letter/s/df788c/32.png) [@Sigene](https://boards.straightdope.com/u/Sigene)\ **Post date:** [May 13, 2005, 12:25pm UTC](https://boards.straightdope.com/t/why-doesnt-soot-burn/303634/10 "2005-05-13T12:25:39Z")
carbon will oxidize given the right conditions. Take a blow torch with a light blue flame (no yellow) and it will burn the soot off. Even diamonds burn…I’ve done it myself. ---
**Author:** ![Rayne\_Man](https://avatars.discourse-cdn.com/v4/letter/r/df705f/32.png) [@Rayne\_Man](https://boards.straightdope.com/u/Rayne_Man)\ **Post date:** [May 13, 2005, 12:30pm UTC](https://boards.straightdope.com/t/why-doesnt-soot-burn/303634/11 "2005-05-13T12:30:01Z")
> [@Sigene](#): > > carbon will oxidize given the right conditions. Take a blow torch with a light blue flame (no yellow) and it will burn the soot off. Even diamonds burn…I’ve done it myself. I wish I was rich like you ! ---
**Author:** ![scm1001](https://avatars.discourse-cdn.com/v4/letter/s/c4cdca/32.png) [@scm1001](https://boards.straightdope.com/u/scm1001)\ **Post date:** [May 13, 2005, 5:16pm UTC](https://boards.straightdope.com/t/why-doesnt-soot-burn/303634/12 "2005-05-13T17:16:35Z")
soot will burn, but its very much harder to sustain a flame so it tends to go out without added heat. this is because most self sustaining carbonaceous flames have to release a gaseous product (while being heated by its own flame) which does most of the subsequent burning in the flame. Soot being almost pure carbon does not release any gas on heating and cannot sustain a flame. ---
**Author:** ![Shalmanese](https://avatars.discourse-cdn.com/v4/letter/s/45deac/32.png) [@Shalmanese](https://boards.straightdope.com/u/Shalmanese)\ **Post date:** [May 13, 2005, 5:49pm UTC](https://boards.straightdope.com/t/why-doesnt-soot-burn/303634/13 "2005-05-13T17:49:46Z")
C + O[sub]2[/sub] -\> CO[sub]2[/sub] No? Pure carbon burnt in the presence of oxygen should release CO2 gas. ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [May 13, 2005, 6:11pm UTC](https://boards.straightdope.com/t/why-doesnt-soot-burn/303634/14 "2005-05-13T18:11:49Z")
Indeed. I believe aq solid chunk of soot :dubious: ignited in a pure oxygen atmosphere would produce flameless incandescence until the carbon is completely oxidized into CO2