From: John De Armond
Subject: Re: Winter Firewood
Date: Fri, 15 Dec 2000 16:34:35 -0500
> Keep a couple of those auto/truck type safety flares nearby and a CO2
> fire bottle. The draft created by the chimney fire will pull the CO2
> up the chimney and should extinquish the fire. IF it doesn't, light
> off one of the flares and pop it into the fireplace. (Tip from our fire
> department on both of these. Oh yeah, call the fire department first.
Another instance of a dumbass fireman stepping into an area where he
knows nothing. That is horrible advice.
Road flares consist of a mixture of either sodium nitrate
(saltpeter) or potassium perchlorate, sulfur and a little strontium
nitrate (for that beautiful red color). None of these ingredients
nor their products will have any effect on the chimney fire. At
best it will do nothing. At worst it will make the fire burn
hotter. As usual, the fireman took a wild-assed swing in the dark
and got close. There IS a product that LOOKS like a roadside flare
but contains fire extinguishing chemicals that IS designed to snuff
chimney fires but ONLY on airtight stoves that can be closed off to
starve the fire of oxygen. These sticks are NOT labeled for use in
a fireplace and probably will NOT work.
CO2 fire extinguishers will NOT put out a chimney fire. Been there,
done that, still have the soot. The draft is sufficiently high that
the CO2 is drawn up faster than a conventional CO2 extinguisher can
discharge it. The CO2 is not persistent and it offers no cooling so
even if the flames are snuffed, the heat remains and will rekindle
the fire as the CO2 passes through.
I used to heat 100% with a homemade central wood fired condensing
furnace and I've had a bunch of experience with chimney fires. A
condensing furnace cools the flue gases below the dew point so that
moisture and gunk condenses out. It is the most efficient design
but it also produces a LOT of creosote in the chimney. I designed
the furnace and chimney to withstand a chimney fire so that I could
simply burn out the creosote. I still needed to control the chimney
fire. I installed a water misting nozzle in the chimney that
directed a very fine mist of water up the chimney. I could almost
instantly extinguish a chimney fire with this device (whereupon the
chimney looked like a steam locomotive under full power) or I could
control the fire. This was very important, since when the flames
jumped 10 feet or so out the top of the chimney, my neighbors tended
to call the fire department which was inconvenient.
Since most people won't have this system installed in their
fireplaces, my backup system is more appropriate. The backup system
is simply a large (10 lb) dry chemical fire extinguisher and the
ability to tightly close the flue damper.
The dry chemical does 3 things. One, it decomposes in the fire and
releases CO2 to smother the fire. Second, it cools the fuel.
Third, it melts, adheres to and coats the fuel with an impervious
coating that prevents rekindling. My procedure for extinguishing a
flue fire, one I tested several times to make sure it worked, was
simply to hose down the fire box with the dry powder, directing it
toward the flue outlet as much as possible. Then simply close and
seal both the draft and flue damper as tightly as possible. This
helps the dry powder smother the fire by cutting off the air supply.
What you do NOT want to do is rush up on the roof with a water hose
and douse the chimney. When the hot chimney cracks or explodes from
contact with the water, what was a serious situation instantly turns
into a clusterf*ck of the first order. If you lack any other tool,
a heavy blanket soaked with water and tossed over the chimney outlet
will smother the fire - and do thousands of dollars of smoke damage
to the house.