070509-16
VISTA and CLASSIC-C
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5055.3
CREOSOTE FORMATION AND NEED FOR REMOVAL
CHIMNEY FIRES
The result of excessive creosote buildup is a chimney fire.
Chimney fires are dangerous. Chimney inside temperatures
can exceed 2000° F. This causes much higher than normal
temperatures in the chimney and on its exterior surfaces. Thus
ignition of nearby or touching combustible material is more
likely during a chimney fire. Proper clearances are critical
during such a fire.
Chimney fires are easy to detect; they usually involve one or
more of the following:
-Flames and sparks shooting out of the top of the chimney
-A roaring sound
-Vibration of the chimney
IN CASE OF A CHIMNEY FIRE
1. Prepare to evacuate to ensure everyone's safety. Have a
well understood plan of action for evacuation. Have
a place outside where everyone is to meet.
2. Close air inlet on stove.
3. Call local fire department. Have a fire extinguisher handy.
Contact your local municipal or provincial fire authority for
further information on how to handle a chimney fire. It is
most important that you have a clearly understood plan
on how to handle a chimney fire.
4. After the chimney fire is out, the chimney must be cleaned
and checked for stress and cracks before starting another
fire. Also check combustibles around the chimney and the
roof.
AVOIDING A CHIMNEY FIRE
There are two ways to avoid chimney fires:
1. Do not let creosote build up to a point where a big chimney
fire is possible.
2. Do not have fires in the heater that may ignite chimney
fires. These are hot fires, such as when burning household
trash, cardboard, Christmas tree limbs, or even ordinary
fuel wood; (e.g.. with a full load on a hot bed of coals and
with the air inlet excessively open.)
W
hen wood is burned slowly, it produces tar and other or-
ganic vapours, which combine with expelled moisture to form
creosote. The creosote vapours condense in the relatively
cool chimney flue of a slow burning fire. As a result, creosote
residue accumulates on the flue lining. When ignited, this
creosote makes an extremely hot fire. The chimney connec
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tor and chimney should be inspected at least once every two
months during the heating season to determine if a creosote
buildup has occurred. If creosote has accumulated, it should
be removed to reduce the risk of a chimney fire.
1. Highest smoke densities occur when a large amount of
wood is added to a bed of hot coals and the air inlet is
closed. The heated wood generates smoke, but without
ample air, the smoke cannot burn. Smoke-free, clean burn-
ing requires small fuel loads, two or three logs at a time
or 1/4 to 1/2 of fuel load and leaving the air inlet relatively
wide open, especially during the first 10 to 30 minutes
after each loading, when most of the smoke generating
reactions are occurring. After 30 minutes or so, the air
inlet can be turned down substantially without excessive
smoke generation. Wood coals create very little creosote-
producing smoke.
2. The cooler the surface over which the wood smoke is
passing, the more creosote will be condensed. Wet or
green wood contributes significantly to creosote formation
as the excess moisture that is boiled off cools the fire, mak
-
ing it difficult for the tars and gases to ignite, thus creating
dense smoke and poor combustion. This moisture-laden
smoke cools the chimney, compounding the problem by
offering the smoke the ideal place to condense.
In summary, a certain amount of creosote is inevitable
and must be lived with. Regular inspection and cleaning
is the solution. The use of dry, seasoned wood and ample
combustion air will help to minimize the buildup.
