201213-20
5
Creosote
Formation and Need for Removal
When wood is burned slowly, it produces tar and other
organic vapours, which combine with expelled moisture
to form creosote. The creosote vapours condense in the
relatively cool chimney fl ue of a slow burning fi re. As a
result, creosote residue accumulates on the fl ue lining.
When ignited, this creosote makes an extremely hot fi re.
The chimney connector and chimney should be inspected
periodically (at least once every two months) during the
heating season to determine if a creosote buildup has
occurred. If creosote has accumulated (3 mm. or more), it
should be removed to reduce the risk of a chimney fi re.
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
burning 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 fi rst 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 signifi cantly to creosote
formation as the excess moisture that is boiled off
cools the fi re, making it difficult for the tars and gases
to ignite, thus creating dense smoke and poor combus-
tion. 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 clean-
ing is the solution. The use of dry, seasoned wood
and ample combustion air will help to minimize the
buildup.
Chimney Fires
The result of excessive creosote buildup is a chimney fi re.
Chimney fi res are dangerous. Chimney inside tempera-
tures 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 combusti-
ble material is more likely during a chimney fi re. Proper
clearances are critical during such a fi re.
Chimney fi res 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 fi re department. Have a fi re extinguisher
handy. Contact your local municipal or provincial fi re
authority for further information on how to handle a
chimney fi re. It is most important that you have a
clearly understood plan on how to handle a chimney
fi re.
4. After the chimney fi re is out, the chimney must be
cleaned and checked for stress and cracks before
starting another fi re. Also check combustibles around
the chimney and the roof.
- The services of a competent or certifi ed installer, (certifi ed
by the Wood Energy Technical Training program (WETT)
- in Canada, Hearth Education Foundation (HEARTH) - in
U.S.A.,) are strongly recommended.
Avoiding a Chimney Fire
There are two ways to avoid chimney fi res:
1. Do not let creosote build up to a point where a big
chimney fi re is possible.
2. Do not have fi res in the heater that may ignite chim-
ney fi res. These are hot fi res, 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.)
