How Hot does the inside of an outside chimney need to get in order to start a creosote chimney fire? Any ideas of what the true or near temperature is? Thanks all...
Creosote fire!....
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The only important thing to keep in mind is that when they do burn, they can be in excess of 2,000 degrees Fahrenheit. That is darn hot, and why they are / should be so concerning.
That said, if there is nothing in the flue to burn, the temp is a non-issue other than possible fatigue on the materials from being overfired.
Nobody can say at X temp you will have a chimney fire. Many variables involved.
pen
That said, if there is nothing in the flue to burn, the temp is a non-issue other than possible fatigue on the materials from being overfired.
Nobody can say at X temp you will have a chimney fire. Many variables involved.
pen
Ok, lets say creosote is in chimney, what will set it off? If the flue is at 400, would that do it? Is that a safe number? Just trying to understand..... Thanks Pen...
If the stove was smoldered for weeks/months, one hot burst from someone throwing some cardboard in the stove might set things off before the outside ever registered any high number.
Keep things under about 475 measured 12 to 18 inches above the stove on single wall pipe, as a general rule.
pen
Keep things under about 475 measured 12 to 18 inches above the stove on single wall pipe, as a general rule.
pen
Actually, this is an excellent question . I have wondered the same thing. What ACTUALLY sets off or causes the fire? Is it a certain temp? Is is a spark?
Good question OP.
I know many here will have great answers.
Good question OP.
I know many here will have great answers.
Of the last chimney fires I have personal experience with (knowing the people involved) all were either trying to use the stove as an incinerator to get rid of some cardboard (or Christmas wrapping paper), or else forgot to close a cracked door left open to let a fire get started, forgot to turn the air down, etc.
The other point to raise, is all involved were burning wood that was not as well seasoned as it should have been, and all did not clean the chimney as often as it should have been for the way they used the stove.
None had a problem until that day where things got hotter than normal. Considering the circumstances, I'd say it's a combination of high temps and with a crazy fire going flames / sparks (especially from cardboard) getting around the baffle and helping to set things off.
Bottom line, burn right, keep the pipe clean, and on that day things do accidentally get out of hand there is nothing to worry about, as the system can handle it. However, even poor practices that never resulted in a fire in 5,10,20, etc years, could do it in one rare instance when things get out of hand.
I know folks who I almost guarantee would have a chimney fire if I were to give them a wheel barrow load of my well seasoned wood. They wouldn't have a clue how to run their stove with well dried fuel. They have been OK for years because they consistently burn such poor fuel that they consistently keep the flue temps too low to have a chimney fire, even though the fuel is right there and ready to go inside the chimney.
pen
The other point to raise, is all involved were burning wood that was not as well seasoned as it should have been, and all did not clean the chimney as often as it should have been for the way they used the stove.
None had a problem until that day where things got hotter than normal. Considering the circumstances, I'd say it's a combination of high temps and with a crazy fire going flames / sparks (especially from cardboard) getting around the baffle and helping to set things off.
Bottom line, burn right, keep the pipe clean, and on that day things do accidentally get out of hand there is nothing to worry about, as the system can handle it. However, even poor practices that never resulted in a fire in 5,10,20, etc years, could do it in one rare instance when things get out of hand.
I know folks who I almost guarantee would have a chimney fire if I were to give them a wheel barrow load of my well seasoned wood. They wouldn't have a clue how to run their stove with well dried fuel. They have been OK for years because they consistently burn such poor fuel that they consistently keep the flue temps too low to have a chimney fire, even though the fuel is right there and ready to go inside the chimney.
pen
Flame impingement is the most common cause of chimney fires. Pipe gets a coating of creosote in the connector pipe or chimney smoke chamber and flame gets to it and it is off to the races.
I did this with my old insert in the back yard a few years ago to show you what happens in the pipe when you toss those pizza boxes in the wood stove.
![[Hearth.com] Creosote fire!....](https://www.hearth.com/talk/data/attachments/119/119386-67dbed983626263b257e199397161c34.jpg?hash=QyNywHS1qY "[Hearth.com] Creosote fire!....")
I did this with my old insert in the back yard a few years ago to show you what happens in the pipe when you toss those pizza boxes in the wood stove.
Nick Mystic
Minister of Fire
The only chimney fire I've had was due to burning some cardboard cereal boxes in my stove in the summer just to get rid of them. Creosote had flaked off from my stove pipe and gathered in a 90 degree elbow near the back of the stove. This is why I always cringe when I read about people trying to save a few bucks and installing an elbow instead of a T-connector when they are attaching a free standing stove with a rear collar. When you don't have a place for creosote to go when it flakes off your liner you are asking for problems when it gathers in that bottom elbow. Once a small pile of the creosote lights off you are almost guaranteed of having a chimney fire if you have any creosote still in your flue.
I've always wondered about this too! With my insert I take the flue temp about 6" up so it shows a much higher temp than the numbers everyone throws around for 18-24" up the pipe. I'm never sure what my "real" flue temp is. I took a pile of my "spoils" from a chimney cleaning and hit it with my MAP torch until I got bored, probably 2-3 minutes of a 3500* flame and it just glowed a little, it never lit off. However this was crunchy flaky stuff, not the sticky glaze. Luckily I've never found any of that stuff in my flue, maybe someone else here can scrape some off and get it to light? For science!
Edit: I am sure there is some on the underside of my chimney cap, I will try it and report back.
Edit: I am sure there is some on the underside of my chimney cap, I will try it and report back.
Nick Mystic
Minister of Fire
I'm all for scientific inquiry, but I'll caution you to wear suitable safety equipment like goggles and non-flammable clothing before you go too far with this. I've read that creosote when it lights off reacts like popcorn in that its size expands exponentially and quite fast. You don't want any fiery hot residue spewing onto you (think hot tar) as you run for a water hose!
Read Pens post again. His quoted temp was for a single wall surface reading. Your double wall (probe) reading is a different critter. I often take my double wall pipe (with probe thermo) to 800F.
ETA: I am with BroB on the flame impingement. Also the location of the gunk will make a big difference. The gunk stuck at the top 3 ft of your pipe will take much more heat (stove heat) to light off than a pile of gunk in a 90 degree elbow 4 ft from the stove body.
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Boy we need a nomenclature for these flue temps, external, internal, double wall, single wall all gets a little confusing after a while.
That is why you will often see me ask for clarification (surface or probe)....and double wall surface temp has no "real world" application in my opinion.
Spinny
New Member
- Dec 26, 2012
- 83
There are small "chimney fires" every time you burn, you just don't realize it. The problem arises when a stove has been allowed to burn on very low heat/smoldering which allows creosote to accumulate for an extended period of time. Then a hot fire happens and it all goes up in flames. The key is to burn you stove HOT once a day, this will help keep your creosote burnt off and not as easily accumulate. There is no substitute for regular cleaning.
looks like the North Korean's first attempt at an icbm , guess they didnt put fins on the rocket
The answer isn't the old wives tale of once a day hot fire. The answer is don't use wet wood and don't ever smolder in the first place.
And for the record, there is never a small chimney fire when I burn.
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Machria
Minister of Fire
Machria
Minister of Fire
Unless of course you hae a CAT stove, which has no issues with smoldering wood. And for the record, the PH does pretty good with wet wood, not that we should burn it, but......
As most know by now this burn hot in the morning and burn off the sote stuff makes me crazier than nature did. One advantage of the two piece baffle, the only one, in the 30-NC is that anytime the stove is cold and the urge strikes I can slide one side of it on top of the other side and using a mirror and flashlight look up the pipe. And in seven seasons, including today, I have never seen any creosote in the pipe. After long night burns.
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Cat stoves are an even better example. Who needs a "hot fire once a day" when 1600 degree exhaust has been blasting out of that cat all night?
Whoa
! Just a bit of mis-information here. Like BrotherBart, this burning hot once a day is old stuff that just does not cut the mustard. Burn good fuel and you won't have creosote. This is why we can go years before cleaning our chimney; it simply stays clean but we don't do the hot fire bit and never have.- Status
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