Chimney Fire Paranoia

[Reid Neilsen]

Not sure if this belongs here or in the "Forges" section of this forum, but here goes:

I am totally paranoid about chimney fires:o Help!

I am curently using an 8" triple-wall chimney system that extends three feet above the roof line(all metal roof with 2x4 rafters/tresses) and comes out right about at the ridge line of the roof(just to the edge of it). The chinmey from the ceiling box to the cap is only about seven feet long. It claims to be a "all-fuel" type chimney and is rated for temps in excess of 2800 degrees for very short stretches. I think I am ok, in that I made sure when I installed it, that there is no combustible surfaces within 6 to 10 inches of the chimney itself(no studs, beams, insulation, etc.) I just use sinlge wall stovepipe to run from the forge hood to the ceiling box. This chimney makes a LOT of noise, small clinks, ticks, etc.(kind of sounds like crackeling:confused:) when in use and it just scares the heck out of me! I can only assume it is the sheet metal expanding and contracting or something under changing temps. It is in an un-attached garage type workshop that is single story. Coal residue is very thick and I clean it regularly with a brush. Having not had lot of experince in chimney building I often wonder is there is a flaw which could cost me my shop.

I also installed two 12" attic vents at either end of the attic space - to allow adequate ventilation in the space, but the silly thing makes me nervous - so nervous in fact, that I have actually taken down plywood ceiling panels when it was making noise one night just to see if there was soemthing on fire up there above the ceiling. Of course there wasn't and it seemed nice and cool up ther due to the attic vents.

PS I have a fire extingusher on hand next to the forge, but that does me no good if soemthing has caught fire due to heat between the ceiling and the roof.

Am I too paranoid? What are your thoughts? Any advice on the subject?

Edited May 14, 2009 by Reid Neilsen

[Charlotte]

You seem a little over concerned. The bottom line here is that if the flue is cleaned regularly and no build up is allowed your construction is more than adequate.

When I lived in East Tennessee many of my friends lived out in the country with coal fired heating systems and little or now maintence. Most of the fires I read about in the area were started by antique wiring or some one smoking in bed.

[Frosty]

Yeah, you're a little too paranoid here. Coal fires don't develop the kind of heat wood does so you'll get soot build up more quickly. Keep it cleaned out on a regular basis and you'll be fine.

I used a gold pan for the roof cap on the house and a SS salad bowl on the shop stack. You may not be able to get away with something like this where you are though. The caps I put on mine have no spark arrestor screens and so the chimney brush will pass all the way to open air and clean it completely. If you have to use a spark arrestor cap brush it from above.

Clean it regularly and you'll be fine. A lot of the pinging and tinkling is the creosote breaking loose as the stack comes up to temp. And the stack cooling down after the fire goes out. If you keep it reasonably clean you shouldn't have any problems. Nobody can give you a 100% guarantee though so be careful and keep an eye on it just like any other appliance using fire.

For the record, we almost lost our house to a stack fire about 4 years ago. We'd had the chimney sweep out about two (2) weeks earlier and they'd pronounced everything in good order. In that two weeks the catalytic converter on the wood stove failed and the stack got a good coat of creosote.

In his diligence to make everything "right" the sweep ran a couple screws through the telescoping double wall into the collar on the stove causing a finger width gap in back out of sight. Wellllllll, this LOOKED good unfortunately it wasn't good in reality. It meant the stack had an uncontrolled fresh air draft to it so as soon as it got hot enough it lit up and couldn't be shut down with the stove's draft.

Deb called me at work, I told her what to do and how to do it then told her to call 911 while she did it and got off the phone. She saved the house while the FD was getting there. Less than 6 mins response time and they double checked everything. Deb done good.

However, anyone else and my ONLY advice is GET OUT and call 911. Being Deb, I knew there was NO WAY she would leave the animals in the house BUT if she were at the stove fighting it she would be within 6' of the front door if she couldn't stop it. Her Father is a retired fire fighter so all I could do is HOPE she would leave rather than go deeper into the house and try collecting the critters. I HOPE he trained her better than that but I haven't asked.

One last thing, we replaced the catalytic stove with a new Jotul (pronounced Yotul) multiple burn zone wood stove. NO catalytic converters . . . EVER again.

Frosty

Edited May 14, 2009 by Frosty

[unkle spike]

Does burning Coal even produce Creosote? I was under the impression that creosote was produced by burning wood, the sap turns to steam in the smoke, and when it hits a cold chimney flue it turns back to sap, and this combined with the smoke particulate clogs the chimney, and with that combination is combustable.

Bottom line, inspect and clean your chimney. I think you are spot on keeping combustible materials away from the chimney during construction. I have a thermometer in my Overhead style hood, the hottest I have seen it was 400 degrees, so I would imagine the flue could be that hot.

That said, I don't think you can ever be "too safe".

[firebug]

What you have described sounds fine. I have investigated and responded to many house fires caused by chimneys. Often it is because they had an opening either from bad mortor joints or bad steel joints. This allowed the hot gases to escape into the chase area igniting the surrounding combustibles. Every so often we would have one caused by the build up of creosote in the chimney liner. You will not experience much creosote build up in a forge as compared to a wood burning fire place. Most of the moisture and particulates are gone by the time we shovel the coal into the forge. People who burn wood with a lot of moisture or soft woods like pine are asking for it. Burn hard wood like oak and hickory, they do not have the resin like pines do. I have been fighting fire before and watched the pine resin flowing down the burning wood inside a house fire. It was burning like gasoline. When you burn pine in a fireplace the resins and soot deposite more readily on your chimney wall as they cool when they rise. The build up can reach its ignition temperature and ignite. When it does it sucks in air like a turbine often causing a roar. The best way to extinguish the fire is to bust an exstinguisher in the fire place. The hot gases and suction will make the water or chemical rise and cool it below its ignition/combustion temp. Once the fire is extinguished or blacked out, get the fire department on the way and check for extinsion into the attic. This of course depends on whether or not you are afraid of fire. If you are afraid of fire just call 911 first.

This response is to the question of whether there is a fire hazard. As to whether the diameter is enough, I am not an expert on that. Mine is 12 inch square stainless steel exiting a metal building with plenty of incoming air.

Edited May 14, 2009 by firebug
add info

[Glenn]

Most opinions are that 8 inch stack is minimal or too small, with 10 or 12 inch being preferred for a solid fuel forge. Not to say it will not work, just to say it is not optimum size. 8 inch chimney has 50 square inches of cross sectional area, 10 inch has 78 square inches of cross sectional area, and 12 inch has 113 square inches of cross sectional area. Just some numbers to play with (grin).

I will relate what I have learned from burning 15-20 cords of wood per winter. A large slow fire will produce creosote. A small hot fire will produce much less to very little creosote. Type of wood, moisture content etc all play a part.

You MUST have more air entering the building than what is going up the chimney for the chimney to draw. The ventilation fans may be produce a negative pressure in the room. You must replenish ALL of the exhausted air and then some. This may mean you have to leave a door open all the time.

Look at the smoke (exhaust) coming from the top of the chimney. If you see much more than a blue wisp (my set up) then the fire is NOT burning correctly, either not hot enough, not fast enough, not enough air, or something. This is true for both the coal forge and the wood forge.

I would err on the side of caution and find the cause of the creosote build up, the cause of the noises, and monitor the situation closely. Change only one thing at a time so you can record the results that change makes. Be sure to build and run the same size and type of fire in the forge during your research. Start with looking at the top of the smoke stack and seeing what is being exhausted under your present set up. Then try getting more air into the room and look at the top of the chimney for changes. Then make one more change and record the results.

[Reid Neilsen]

Thank you for the advice on the subject. After posting that, I am feeling a little better about the whole thing. I can freak myself out about things like this!

As for the 8 " thing, I couldnt agree more, I don't have a problem getting it to draw because I always have good influent airflow into the shop. It is drafty and I often keep door or window cracked. In the summer I just jeep the big bay doors open. If I had it to do over again though, I'd go with a bigger chimney. The 8" is definitely at the lower limit of what seems to work. I, not knowing better, went with it because it was the size that my forge hood attached to and I thought that was big enough. (D'oh!) Thankfully I have never had a problem with it drawing. I also have no screening or spark arrestor on the cap (I figured that it was not as necessary as it would be on a wood stove chimney and would just clog more easily with the coal soot).

I just need to knock out that residue pretty frequently and I think I probably should not have much to worry about. This is just all new stuff to me - thanks for the advice.

[rokshasa]

man if you seen what i was using you'd let it go lol

[dablacksmith]

man if you seen what i was using you'd let it go lol

ya or what i ran in the past for my portable ... the stovepipe (single wall) went right thru the top of my tent (granted it was sunforger) no gaskets just a slit in the canvas ... never a problem cause there was never enuf heat... at the worst highest heat i could still touch the stovepipe .. it was warm but not burning hot (granted i got calouses) . forges dont seem to build the heat in the chimney . I would be more woried about buildup and getting that burning tho i dont know how the creasote would ignite ... think it takes a bit of heat for that to happen .. i know the museum where i setup shop at were paranoid about it ... been a year and a half they arnt as woried now... have fun

[divermike]

Coal usually is a pretty clean burner, I have never heard of a chimney fire in a coal system. But I have inspected thousands of wood units, and several that have suffered considerable damage from creosote buildup fires.

[Sweany]

Why don't you try to burn the coal soot? :)

[saintjohnbarleycorn]

I have never heard of a chimney fire in a coal burning system either, clogging up and suffocating the people in the house but never burning it down. The creosote is a gooey mix that once started burns very hot, like the above poster says try burning the soot and see what happens.
I have burned all types of wood in my house, and built a rumsford fireplace/insert, burned for over thirty years and have never once cleaned the chimney. I check it with a mirror and it is always clean. IT is not air tight by any means or that efficient and the chimney goes right up the center of the house which is insulated and open in the attic. The chimney heats the second floor. So if any creosote is there is doesn't condense on the liner apparently. hope this isn't too off topic. kevin

[Dragons lair]

St John< I lived in the oldist house on the Boston Post road for a yr.
Had an orignal Rumsford fire place X4 Greatist fire place ever Drive you outa the room.
Ken