Chimney fires and forges

[Glenn]

Are chimney fires a concern when using a forge?

We normally associate chimney fires with fire places in the home, and burning wood. But what about burning coal, charcoal, coke etc in the forge? Do these fuels create creosote or other materials that can collect in a chimney and create a fire?

[Ice Czar]

charcoal and coke have had almost all the volatiles already burned out
coal tar however is what is driven out of coal to make coke which is what a coal forge does. if the chimney is long enough, narrow enough, cold enough and given enough time to condense on the lining it can pose a hazard.

A properly designed chimney mitigates those factors and prevents the buildup.
But a more energy efficient exhaust system my reintroduce the potential for condensation, by scavenging the exhaust heat, added maintenance may be required. Monitoring and cleanout ports would be prudent.

the hotter the combustion chamber, the more complete the burn of the fuel, meaning less coal tar in the flue gas to condense
of course a forge isnt like many industrial furnaces which can run continuously with only downtime for maintenance. The more thermal cycling occurs the greater potential for condensation before the combustion chamber gets up to temperature.

[saintjohnbarleycorn]

probably the best thing to do is look up your chimney and see if anything is glomed onto the walls of it. If not you don't have to worry. If so clean it out a bit.

[jayco]

Before 1980, there were still lots of country folk around here who heated their homes with 'house coal'. We burned it ourselves in 'coal grate' fireplaces,pot-bellied stoves, and regular coal stoves. This was before 'the environment', the EPA, and 'pollution' were commonly known terms in rural areas.
Heating the house with coal made white curtains and white ceilings an impossibility.
Every time you opened the stove door to add more coal, or to remove ashes, a cloud of coal dust issued from the open door and settled on everything in the house.
(Sort of like living in a blacksmith's shop........all the time!)
From that time, I do remember having the coal stove 'run away' (burn uncontrollably) a time or two. Other folks also reported similar occurances occasionally.
Whether these 'run away' fires were caused by coal tar in chimneys.......I cannot be certain.
As far as cresoate fires are concerned, they are caused by buildup of cresoate on the walls of chimneys........(burning wet or green wood slowly , often with draft controls closed and/or dampers closed.
Incidentally, the rise in cresoate fires seems to correlate with the rise in popularity of the 'air tight stove'. (Which allowed an eveh slower burn.)
If we had had air tight coal stoves back then, coal tar fires might have been commonplace. This might not be correct, but it does seem plausible.
After all, when you think about it, coal and wood,charcoal and coke, and cresoate and coal tar are not so much different from each other.

[R Funk]

Ice Czar is on the money when he relates the volitales to the "creosote" build up in the chinney. I did not look it up but if I remember correctly wood has 3-5 times as much volitales as coal, Thus wood is more likely to cresote up a chimmey. I would doubt a forge fire would condense volitales like a wood stove, but the chimmey should be checked.

If we allow a wood stove to burn at low heat, as many airtight wood stoves do, the fire is not hot enough to burn the volitales, and they condense on the chimmey. With a hotter fire more volitales are burned in the fire plus the chimmey is hotter and more volitales can pass thru the chimmey without condensing.