What temp starts a chimney fire?

[Battenkiller]

My question is how likely is the creosote that is further away from the stove to ignite spontaneously if there is no chimney fire starting in the section of flue closest to the stove? It seems to my thinking that a chimney fire must start close to the heat source and then continue burning further up the flue. When it warms up for a day in January I pull the lower section of pipe that connects to the stove and brush out all the creosote figuring that my once per year complete clean in the summer will be fine if the first 10 feet are cleaned mid season. Am I wrong with this logic?

I think you're on the right track, but I'm sure not a chimney expert. I'd feel safe enough with that. Of course, it all depends on what you're pulling out of there. If you get 2-3 gallons of flake creosote out of the first 10 feet during your mid-season cleaning, I think you need to get a lot more aggressive. With my setup, I burn extremely hot every day for at least an hour all told. No exceptions ever. I can see right up to my elbow (about 3' up) with a light and mirror from inside my stove when the damper is open. I do this every time the stove is cool enough. On only a couple of occasions have I seen anything but clean metal. Those few times with soot and a bit of creosote in there I could have predicted ahead of time without looking, just by knowing I had had a poor burn the night before. 15 minutes at 600º on the flue pipe thermometer turns it all white again (single wall pipe, magnetic surface thermo).

I don't recommend that anyone try this unless their chimney has been freshly cleaned. An attempt to burn off all the creosote built up over a month long period of cold, wet burns could very likely precipitate the event you are trying to prevent.


As far as sparks and stuff, I really don't have an expert opinion to draw from, but the last time I pulled my pipe and elbow and looked up the flue, I was able to reach up and scrape a small amount of creosote off of the flue walls. I took this stuff - about a tablespoon - and put it on a metal plate and tried to light it with a butane BBQ lighter (this was before I talked to that stove tech). The idea was to show my oldest son how hazardous the stuff was. Best I could do was to get it to smolder and then go out once I pulled the lighter away. I fluffed it up and tried to give it as much air as I could. If some else tries this and gets a different result, put it on video for us all to see. To be honest, mine was about 50% soot and 50% flake creosote, so that may have been a contributing factor, because soot is almost all carbon and is, apparently, very hard to ignite. I'm very curious about all this, because until recently I had assumed it was a lot more flammable than what I am seeing and hearing.

 

[chrisman34]

The key to seeing it at full force is to take a section of pipe down, lay it on its side with a slight angle, stick some paper in it and let it rip! it is truly an amazing show! I too tried lighting a pan of it with a torch and nothing......But the narrowed draft really makes a hell of a fire...trust me, or better yet try it. You may have more soot than creo, and get nothing. But the creo will burn hot and fast in a section of pipe with no air control. I have seen many a house destroyed by chimney fires. I would say 90% of "real" fire calls in my area are caused by chimney fires. Most because the people haven't cleaned in a long time, or just not burning the right stuff.

Think of it this way.....take a couple pieces of wood out to your driveway and light them......they wont burn nearly as well as they do in the confinement of the wood stove....same with the creosote.

 

[mnowaczyk]

You have to worry even more about a chimney fire than other people! If you build up a lot of creosote with your setup, and none of it burns out, yours is the kind that when it finally does burn, and it will someday burn, you will have a large and destructive chimney fire.

Agreed. You bet. That's why I've had a sweep come out and inspect / sweep for about every 3/4 cord that I've burnt. They keep laughing at my fear of a chimney fire, and walking away saying there's not much to clean.

My goal is to clean the creosote out instead of burning it out. Will I still have a chimney fire that way?

If you keep the creosote reasonably cleaned out, you won't have a chimney fire. You are right, that's the best way, aside from preventing creosote in the first place.

Thanks Quads.
If you see my posts, I'm all about figuring out how hot i need to be for no creosote. I'm also all about trying to figure out how to get a liner in this chimney without destroying the damper. I have not figured out the latter. So now I only burn on really cold days and weekends when I can keep the temps up. I burn with wide open air, and do everything to keep all three of my magnetic thermometers reading over 400. The one in the center of the two doors is almost always over 600, and sometimes up to 800... at 800 I back down the air. But this is 200 degress hotter than the other two thermometers, which are where the manual suggests putting a thermometer, and it suggests keeping the temp between 400 and 800. So I'm lucky to hit 600 in those spots. I figure I'm running weel within the stove guidelines. In fact, it takes a little while to get to 400 in those top corners of the stove... so I think the manual suggests running this one really hot. I would guess they want the glass to be 600-1000 degrees. Thus my concern about a chimney fire.

So in conclusion, I should probably not be worried about the temperature causing a chimney fire, but rather flying embers igniting some creosote somewhere in the chimney. I think I've got it now. And if I can only figure out the liner now....

 

[chrisman34]

My chimney fire (thanks for not doing your job mister sweep sir!! @#&^&@!*&#&$@^&) started before it hit 250.....So my guess is there was a spark of some sort that lit it off...maybe flames up the chimney....but it was definitely not heat in my case. I was, and still am to a much lesser degree, paranoid and never left the side of the stove till it was cruising nicely....I also took great care in not letting paper have any chance of escape....still wont burn top down! So it had to be a spark or the flames licking the chimney.

 

[ikessky]

With a cheap Rutland Burn Indicator thermometer on single-wall pipe, the creosote starts to burn at about 450.

For real? On my setup, I usually hit 400-550 every time I reload. I just did a sweep yesterday and all I got was powdery soot, no big chunks of anything. Most of the build up was in the area where the chimney sticks out of my roof. I wonder what will happen when I get some perlite added to my setup this summer.

 

[mnowaczyk]

My chimney fire (thanks for not doing your job mister sweep sir!! @#&^&@!*&#&$@^&) started before it hit 250.....So my guess is there was a spark of some sort that lit it off...maybe flames up the chimney....but it was definitely not heat in my case. I was, and still am to a much lesser degree, paranoid and never left the side of the stove till it was cruising nicely....I also took great care in not letting paper have any chance of escape....still wont burn top down! So it had to be a spark or the flames licking the chimney.

So how long / how much wood was burnt since your last sweep before the fire?

You've got a stove. Does it have no "afterburn" chamber to burn off the smoke? Just a straight shot up the flue? Is your setup lined with stainless steel? Or an old clay lined masonry chimney with a brick and mortar smoke shelf / smoke chamber (like what I have)?

 

[quads]

With a cheap Rutland Burn Indicator thermometer on single-wall pipe, the creosote starts to burn at about 450.

For real? On my setup, I usually hit 400-550 every time I reload. I just did a sweep yesterday and all I got was powdery soot, no big chunks of anything. Most of the build up was in the area where the chimney sticks out of my roof. I wonder what will happen when I get some perlite added to my setup this summer.

Yes, I'm not making it up. The fact that you hit 400-550 every time you reload is part of the reason why you didn't get any creosote when you swept. You're keeping it burned out before it can build up. It's when you go for weeks without ever getting to that temperature that it builds up. Then one day you hit that temperature and it burns out like it normally would, except this time there is A LOT of it to burn out.

 

[mnowaczyk]

Thanks Quads. This makes me feel a lot better to read. I run my insert with a face temp always over 400 at the coldest point on the face of the stove. The hottest point is almost always over 600. On the other hand, I've got a monster flue 13x13, and my stove calls for 8" round.

I've got some interesting pictures to post of the brown snow / slush coming down my chimney. I guess that could be from last night's overnight burn where the face temp got down to about 250.

With a cheap Rutland Burn Indicator thermometer on single-wall pipe, the creosote starts to burn at about 450.

For real? On my setup, I usually hit 400-550 every time I reload. I just did a sweep yesterday and all I got was powdery soot, no big chunks of anything. Most of the build up was in the area where the chimney sticks out of my roof. I wonder what will happen when I get some perlite added to my setup this summer.

Yes, I'm not making it up. The fact that you hit 400-550 every time you reload is part of the reason why you didn't get any creosote when you swept. You're keeping it burned out before it can build up. It's when you go for weeks without ever getting to that temperature that it builds up. Then one day you hit that temperature and it burns out like it normally would, except this time there is A LOT of it to burn out.

 

[ikessky]

Yes, I'm not making it up. The fact that you hit 400-550 every time you reload is part of the reason why you didn't get any creosote when you swept. You're keeping it burned out before it can build up. It's when you go for weeks without ever getting to that temperature that it builds up. Then one day you hit that temperature and it burns out like it normally would, except this time there is A LOT of it to burn out.

In rare cases, I only take it to that temp in the morning and evening, but those times are few and far in between. I was out of town this past week and my wife ran the stove. She actually listened to me when I told her to take it up to 400-450 when she put wood in. Figured I better sweep when I returned just in case though.

 

[mnowaczyk]

You guys think this brown slush muck on my chimney is bad news?

I had a temp of 250 when I woke up to nothing but coals in the morning.

 

[quads]

You guys think this brown slush muck on my chimney is bad news?

I had a temp of 250 when I woke up to nothing but coals in the morning.

No, it's ok. Gunk sometimes builds up on the outside, especially in wet snowy weather. I get big brown icicles sometimes. It's what's on the inside that matters.

 

[chrisman34]

My chimney fire (thanks for not doing your job mister sweep sir!! @#&^&@!*&#&$@^&) started before it hit 250.....So my guess is there was a spark of some sort that lit it off...maybe flames up the chimney....but it was definitely not heat in my case. I was, and still am to a much lesser degree, paranoid and never left the side of the stove till it was cruising nicely....I also took great care in not letting paper have any chance of escape....still wont burn top down! So it had to be a spark or the flames licking the chimney.

So how long / how much wood was burnt since your last sweep before the fire?

You've got a stove. Does it have no "afterburn" chamber to burn off the smoke? Just a straight shot up the flue? Is your setup lined with stainless steel? Or an old clay lined masonry chimney with a brick and mortar smoke shelf / smoke chamber (like what I have)?

Sorry for the delay...been busy.... It had been about a month...3 burns about 8- 10 hours each... small stove..pre epa vermont casting...can't remember the model, but was very small, anyway it was caked with the sticky tar type crap. After the fire I hired another guy to come out, he was very ticked. Very obviouse stage 2 I think he called it creosote. I had him look at my fire place insert which I hadn't burned at all since it was "cleaned"....He removed a 5 gallon bucket worth! Mainly from the smoke shelf. He also stated he would be very carefull using it without a liner!! WTF the other guy never mentioned that! The first guy said I must have used the fire place insert and stove ALOT with bad wood to cause that much creosote! Anyway I hope the guy goes out of business before he kills somebody! I have spread the word as much as I can.....