Had some guys inspect and sweep my chimney when I moved into this house during winter of 2012 and they found some gaps in the mortar between the flue tiles (house built in 1972) and put the fear of God in me about chimney fires.  I'm sitting on some seasoned hardwood and with temps falling I've been doing some open fires to take the edge off the temps.  I was reluctant to build many fires given the warning these guys gave me.

Today a buddy of mine was telling me that chimney fires are not due to the presence of creosote - but THICK build-ups of creosote (like an inch) that occur over long periods of time.  He said if I burn seasoned wood and get it swept every year, even with mortar gaps that I'd be fine.

I know a lot of you guys use wood heat and probably deal with this.  Please educate me.  How serious is this?  How likely to occur?  I can provide any additional details if needed.

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Additional Info:  I'm in the middle east-coast and we usually have mild winters; but one day I'd like to make use of the wood on my property and get a wood stove insert / 6 inch stainless liner to bypass the chimney issues.  Until then, I use my heat pumps and an occasional fire (have 2 fireplaces downstairs, one on each end of house - which do add a noticeable bit of warmth but nothing like a stove).

Your buddy is correct and that's why the gaps in your flue are a problem.  The crevice would allow creosote to build up.  Creosote generally builds up b/c you are burning unseasoned wood or wet wood - both of these will cause incomplete (e.g., cool) burning.  We lived at our previous house for six years and never had the chimney swept - we did check it, but never had a significant build up of creosote.  We always burned seasoned wood and started our fires w/ cedar which burns pretty hot.

Thanks. How does creosote catch - ember hits it and conditions are right?

How often do they occur and is it a material risk?  With so many people who never even bother to change their air filter I gotta think if it was common you'd see them all the time

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Grew up with using only a fireplace for heat.





IIRC, incomplete combustion of wood gases, from a cool fire, allows creosote to condense out of the flue gas onto the wall of the chimney. Then one day you get a hot fire going and the extra heat ignites the built-up creosote.


It sounds like a jet engine, or maybe a rocket going off. The extra heat/fire in the chimney creates a huge updraft, which further feeds the fire.





Then burning embers/chunks of creosote get sucked out the top, land on the house roof and surrounding ground, causing further fires. We were lucky, as we has an asbestos covered roof. Saved the house on several occasions.





The quick way to kill a chimney fire is to block the chimney, cut off the air flow to the fire. Stuff a blanket, jacket, pillow, anything, up the flue, NOW, as soon as you hear the roar. Then get outside and hose down the roof.





Be aware that the fire can burn thru the gaps/joins in the flue pipes, and start a fire in the chimney wall cavity. Think Space Shuttle burning 'O' rings.





Bottom line, keep your chimney clean and inspect regularly, especially if burning pine or softwood. Creosote can build up FAST.
 
 

I burn all sorts of shit wood and I have an old ass insert that leaks around the door.

I sweep my chimmeney at least twice a year and i haven't had any problems, I get about 1/4 inch of soot/creasote build up sometimes, but never more than that.

I also don't burn everyday and it's not my main source of heat, I burn about 3 nights a week.

My Point is, if you keep up on the maintenance, the type of wood matters "less", but that's easy for me to say in Nevada.

You want the fear of god look at what temperature creosote burns at, jaw dropping. We've heated with wood as a primary heat source for almost 20yrs. Have had one chimney fire that I was able to address by closing all dampers and watching an waiting.

Don't burn wet or rotten wood or woods with lots of sap/pitch, don't burn anything but wood and clean the chimney often. I try to hit it once a month .

There are two types of chimneys, those who have had a fire and those that will.

US nails it. Gaps can be catch-alls for creasote but it will usually line the majority of the chimney. The taller the chimney the more likely build up will exist.

If you sweep the chimney and the only creosote is in the cracks - is this still a threat for a major chimney fire?

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While I don't advise doing this, closing off the damper then getting on the roof and putting the water hose to the chimney has been a method of stopping a chimney fire before.  The biggest danger is often the roof is not safe to climb on in the first place.

And you will almost certainly destroy the liner that way, and have a good chance of cracking the masonry in the fireplace.

OP, there are not supposed to be gaps in the mortar between the tile liner sections.  Those gaps will allow smoke, heat, and other byproducts of combustion to get between the liner and the chimney bricks and mortar, where it's not supposed to be.  Aside from the byproducts themselves burning, the changes in temperature alone could cause the brick mortar to fail, and then there's nothing at all to keep the fire out of your attic.  You should get the liner repaired.

FWIW, I'm not a chimney inspector, but I am a firefighter and I put out chimney fires every year, have seen more than a few homes destroyed by chimney fires, and give classes to my FD on chimney fires.  I'm also biased toward "safety first", of course.

Not a hijack, since the subject is chimney fires.








 

I burn wood 3-4 nights a week.  For what its worth I do keep a few of those chimfexs around.

I have been to a few chimney fires back in the EMS days and I don't think it is worth the risk.  We heat exclusively with wood and I clean our chimney (triple wall pipe) four times per year.  We essentially burn 24/7 from October to April, so it is worth the peace of mind to me to clean frequently.

I don't know much about a masonry chimney, but it makes sense to me that if you have gaps creosote will build up in them and if it were to catch fire this is a weak point for flame to extend out of the chimney.

If you are going to use an insert or a woodstove, would a chimney liner not be in order?    My brother put one in, and it came with an high temp insulation kit to help keep the chimney liner hotter.  As I read it, if the chimney liner stays hotter, the gasses can't cool down as fast and AS MUCH creosote can't build up.    I would imagine that some still does, but a chimney liner isn't going to have big gaps where mortar has fallen out.   I'm sure they don't eliminate chimney fire potential completely but help considerably.  

I'd also wonder if a 6" chimney liner would be easier to clean than a larger diameter chimney.   My Father in law just brushes his out once or twice a season, and has never had any problems x 25 years or so.

Quick read:
http://www.rockfordchimneysupply.com/articles.php?article=Do-I-Need-a-Chimney-Liner

I had a fireplace when I lived up north and I had an old timer tell me to throw a handful of salt in a really hot fire every month or so and it will  burn off the creosote. It always seemed to work.

yes also hot fires will not allow it to build- 5 yr in ak, never needed a chimney sweep



ymmv



 

How about those logs you throw in the fireplace that reduce the risk of chimney fires?  Are they any good?

I once had a place with a free standing fire place that had the smoke stack  turn dark red one winter. Had to call the fire department. Scared the shit out of us. One guy stood on the roof with his hose and another guy was inside. They ended up letting it burn itself out and gave me a lesson on fresh wood.

I was young...  Just get a sweep once a year.

Our fire department has two attacks for putting out chimney fires.  The first is to take a CO2 extinguisher and shoot it up the chimney.  The draft carries the CO2 up and out, usually extinguishing the fire.  We also have long chains (aptly dubbed the chimney chains) that we drop down the chimney from the roof and shake around to knock the creosote off.

This usually puts out the fire, but don't forget that if the heat built up enough it can catch the house on fire.  Often the fire extends into the attic space through an access port or gaps in the bricks.

I recently heard that if your gas appliances vent through the chimney their exhaust is corrosive to the mortar.  Over time this leads to break down and gaps.  Nowadays everyone recommends venting everything through a flu.

They generally just burn really hot w/ the idea of clearing out creosote.  Regularly using a hot burning wood, such as cedar, should do the same thing.

Is that what they mean by seasoned wood?  

I spent many years as a firefighter in an area where fireplaces were the most popular form of heating.  We really didn't have that many chimney fires by comparison because the people were pretty conscious of keeping their chimneys clean and in good working order.  Just about every chimney fire we had was the result of the homeowners getting lax on maintenance.  If your chimney has already been inspected and found to have a problem then I wouldn't use it at all until getting a full inspection and a repair or a "good to go" from an expert.

Now, here's a handy tip for anyone who uses a fireplace and chimney...buy a box of quart sized Ziploc bags and go to a fire equipment supply company.  Have them fill the bags with ABC powder.  Then, should you have a fire, get on the roof as soon as possible and toss an ABC bag down the chimney?  The heat will immediately melt the bag and release the powder coating the chimney walls and smothering the fire.  You may have to use multiple bags depending on how bad the fire is.  NEVER EVER use a water hose and spray water in because it will very likely cause severe damage by cracking the interior and requiring a very, very expensive repair.  

We used the "ABC grenades" on almost every fire and they work extremely well.

How do you clean a chimney that has a "turn" in it?

For our wood-stove downstairs, the pipe is angled to reach the chimney, then it makes a 90 degree turn to go into the wall.

HOWEVER, the "turn" I'm referring to is actually in the chimney itself, which makes another 90 degree turn, then a 45 or so - and maybe another to get vertical again!

We don't have a clean-out chamber, like I've seen in other chimneys - just a small space at the base of the chimney itself, at the top of the cinderblock wall it rests on.

Sorry that it's so hard to describe. I've never seen anything like it before!

I'm going to try to get our rope gasket replaced today . . . maybe I can pull out the pipe and snap a pic or something so you guys can better understand WTH I'm talking about!  

FWIW, It's been run really hard/really hot this year and we've got good wood, so if we were gonna have a fire, we'd have had one by now, I'm sure. But, trying hard to be as "prepped" as I can, I'd still like to be able to clean that bitch out myself. The only sweeps I've ever seen were round, made for metal liners - not, for masonry (almost looks like terra-cotta or ceramic of some kind).

Sorry for the hi-jack, but I'm sure I'm not the only one with these questions!

Thanks, in advance.  

I didnt exactly have a fire but i did get it to hot this morning. I started the fire in preparation for the cold snap this morning and while in a rush to get the kid and wife off to school, i left the door open on my wood burning stove. Walked inside and had the burnt creosote smell and my pipe was glowing red. Right out of the stove it makes 2 90* bends so it will line up with the pipe that goes out the roof. That first section is single wall and when it gets out of the 90s, it turns to triple wall pipe.

Single wall pipe was glowing red and the triple wall was just warm to the touch. Invest in the good stuff and a mistake like i made will save your house.

Check your inbox..

Ops

OP I build chimneys and have taken apart many old ones.

Lots of fires burned just fine in those old dry stacked flues with the hollow block, the big thing with chimney fires is improper burn cycles, you can burn freshly cut wood in your chimney if you want ad not have a problem.

The trick is every morning you need to burn your fire hot for 30-45 minutes. Open the flue all the way up and give it all the air it wants and get a nice hot fire going. This will get the chimney hot enough to burn off any sticky creosote from the day before, but there won't be enough accumulation for it to be a threat.

You also need to visually inspect your chimey for blockages, they usually build up right on the seams of the tiles in the corners, and the bigger they get the more dangerous they are. If you are burning very green wood inspect at least once every two weeks, for well seasoned wood just keep a regular burn cycle and peek your head in there when you think about it.

I run a brush down my chimney every month as a precaution, most of the time it doesn't even need it.

That situation sounds interesting, but nothing in impossible. Why anyone would build a chimney without a clean out door is beyond me. It sounds like your best bet would be to order some flexible rods and the proper brush and sweep it from the top down and from the bottom up, then run a shop vac hose up into the 90 degree turn to get out any debris.

Not having a clean-out is indeed idiotic. I agree!

Do you know where I might order be able to a flexible sweep set-up, like you'd mentioned? (I have the shop vac covered at least!)  

From what you said, I bet we're not in too bad shape as it is - even though we've been burning wood for the last three or four years w/o a sweeping - cuz we've done exactly what you suggested to the OP: hot fires to burn away any residual creosote from the low, slow-burn the night before and from any un-seasoned wood that might've slipped through (if any, which I highly doubt).

I'm glad you piped in, bro. I'd asked about burning out the creosote like that before (a few months ago) because friends had said that's the way to do it. Yet, a couple arfcommers said they wouldn't trust that. Having a flexi-brush (like you said) will take away most of our fears - and the threat I'd guess.

And you know, you're the perfect guy to ask this too:

We have large flagstone sections covering our chimney - kinda held together by roofing tar or black adhesive caulk. If it's winter, can I still tear the one section off to access the chimney and reapply the black-goo-stuff when we're done sweeping? I'm mostly wondering if the cold will prevent a good seal. We've had moisture get in during a prolonged, cold rain this year (cuz it's not in the greatest shape currently) and steam was actually coming from where the pipe goes into the wall! I climbed on the roof to be sure that's what it was and there was a shit-load of water droplets on the bottom of the flagstone (and chimney interior) and it seemed like more was being created as the chimney heated up from the fire below!

I'm sure some of the condensation is just from warming the cold masonry (the fire had been neglected the night before and gone out), but that sealer is in bad shape so it'd probably be wise for me to fix it - if I can, given the weather. Agreed?

Thanks a lot for your input, bro! It's much appreciated!

Start here for ordering brushes and rods.

http://www.northlineexpress.com/chimney/chimney-brushes/how-to-choose-a-chimney-brush.html

As far as the second question I am having trouble picturing what you are describing, why do you need to remove the veneer to sweep the chimney?

Some of the trucks in my FD carry the ABC grenades as well, but in a plastic grocery bag instead of a Ziploc bag.  My company's practice has always been to carry a salvage cover into the house and set it up in front of the fireplace, then discharge an ABC extinguisher up the chimney.  The draft helps carry it up, and the salvage cover prevents a mess in the living room from any that comes back down.  Someone earlier in the thread mentioned CO2 extinguishers - it's a moot point for me since my FD doesn't carry them, but I'd be worried about the CO2 (which comes out very cold) damaging the flue liner.  Clay liners can endure extreme temperatures that exceed normal operation temperatures and even chimney fire temps - they crack when there is a rapid temperature change.

OP, here are a few excerpts from a document I read the last time I was studying up on chimney fires:





Damage and liner gaps can become a source for more damage.

Chimney Fires: Causes, Effects and Evaluation .pdf

That is interesting.

I always make it a point to use as extra heat stop on each flue and then use a sponge or rag to smooth out the inside where it squeezes out. I never really thought of air getting in and making a chimney fire worse, I do it to keep creosote off the concrete block to prevent it from premature rot.

Flue tiles are kind of a bastard, none of them are the exact same size and they are often not totally squared off either, I have taken apart old chimneys where the entire liner was just leaning against one side of the block, I bet that would be a prime candidate for the air in the gaps you were talking about.

Craziest thing I have ever seen as far as chimneys go was a house built in the 1800's. The chimneys weren't original, but they were still very old. Each bedroom upstairs, 3 total, had a hardwood shelf boxed out and attached to the wall, then there was a small concrete pad on top of the shelf and the old fashioned cinder blocks going right up through the ceiling with no liners.

I assume each one had a small wood stove hooked into it for sleeping in the winter. There was so much creosote up inside the rafters and roof sheathing that you would have thought the place was on fire recently, no actual sign of fire though, just years of leaky unlined block.

I absolutely agree with the "No" water idea!

Wanna wash creosote or carbon sludge into your house as well as cracking the liner/firebrick?

Might I add that if its cold enough to be heating with wood isn't there a SLIGHT chance your hose will be froze anyway?

Just sayin' its best to prevent than treat in this case. YMMV

This is what I was told to do incase of a chimney fire, open the flue and rake around the coals in the stove, then put on gloves and a facemask and toss one or two cups of water in and shut the door. The steam going up through the chimney has a chance of putting out the fire.

The first year in my house I had a chimney fire in our stainless triple wall ( I am a mason without a proper chimney) and I went outside to see it snowing black. In my haste to stay warm I forgot to inspect the chimney after we moved in ad just lit a fire.

Anyway, I did as mentioned above and it went out, the fire wasn't terribly big, it probably would have burned out on it's own in short order.