
Chimney Smoke and Creosote
Formation
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 ue of a slow burning re. As a result, creosote
residue accumulates on the ue lining. When ignited, this
creosote makes an extremely hot 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 re.
1. The highest smoke densities and emissions 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 smaller 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 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 signicantly to creosote
formation as the excess moisture that is boiled off cools
the re, making it difcult 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 annoying smoke
emissions and creosote buildup.
Chimney Fires
The result of excessive creosote buildup is a chimney re.
Chimney res are dangerous. Temperatures inside the
chimney can exceed 2000° F(1093˚C). This causes much
higher than normal temperatures on its exterior surfaces.
Thus ignition of nearby or touching combustible material is
more likely during a chimney re. Proper clearances are
critical during such a re.
Chimney 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 the event 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 replace.
3. Call local re department. Have a re extinguisher handy.
Contact your local municipal or provincial re authority
for further information on how to handle a chimney re.
It is most important that you have a clearly understood
plan on how to handle a chimney re.
4. After the chimney re is out, the chimney system must be
cleaned and checked for damage before starting another
re. Have the system inspected by a certied installer
orchimneysweep.Also check combustibles around the
chimney and the roof.
Preventing a Chimney Fire
There are three things you can do to prevent chimney res:
1. Do not let creosote build up to a point where a chimney
re is possible.
2. Do not have res in the heater that may ignite chimney
res. These are very hot 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 control open for long period
of time.)
3 Regular inspections and cleaning.
- The services of a competent or certied installer, (certied
by the Wood Energy Technical Training program (WETT) - in
Canada, Hearth Education Foundation (HEARTH) - in U.S.A.,)
are strongly recommended.
Wood Selection
This heater is designed to burn natural wood only. Higher
efciency and lower emissions generally result when burning
air-dried seasoned hardwoods, as compared to softwoods
or to green or freshly cut hardwoods.
Wood should be properly air dried (seasoned) for six months
or more. Wet or undried wood will cause the re to smoulder
and produce large amounts of creosote. Wet wood also
produces very little heat and tends to go out often.
Do not burn anything but wood. Other fuels, eg. charcoal,
can produce large amounts of carbon monoxide, a tasteless,
odourless gas that can kill. Under no circumstances should
you attempt to barbecue in this heater.
How to Test Your Wood
Add a large piece of wood to the replace when it has a large
hot bed of coals. It is dry if it is burning on more than one
side within one minute. It is damp if it turns black and lights
within three minutes. If it sizzles, hisses and blackens without
igniting in ve minutes it is soaked and should not be burnt.
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