Cr
eosote - Important Woodburning Information
Cr
eosote is the tar-like substance that forms on the heat
exchanger, flue pipe and chimney when burning wood.
Wood combustion is never complete, a visible sign is
smoke coming from your chimney.
Wood when freshly cut can contain as much as 50%
moisture, depending on the type. Air dried wood, when
under ideal conditions, will still contain approximately
20% moisture. The moisture, along with flue gas prod-
ucts, are vented outside by way of the flue pipe and
chimney. Flue gas products, when chilled, condense into
liquid creosote which may become a crystal (solid form)
as temperatures increase with heat requirements.
The heat control method on furnaces when burning
wood, is the size of the fuel charge along with the control
of combustion air, to increase or decrease the rate of
burning which governs the heat output.
To help prevent creosote in both grate and base burners,
burn dry seasoned wood, hard wood is more desirable
than soft wood. Govern your wood load with the heat
output required. Spring and fall require frequent small
charges. A small intense fire produces less creosote.
Short flue pipe runs help to keep the gases above the
dew point.
The interior chimney holds and retains heat longer result-
ing in less condensation than the exterior chimney.
A good draft produces a hotter fire and exhausts the flue
gases outside more rapidly at higher temperatures pre-
venting condensation of flue products.
A combination furnace in need of cleaning, will have poor
draft creating a lazy fire and eventually, if ignored, may
smoke around the doors when the oil side is running with
wood fire. (Poor draft in a clean system can also produce
smoking around the door). This choked condition with
soot and creosote can only be relieved by cleaning the
entire system as frequent as necessary, if neglected it will
cause a chimney fire, which could result in property loss
and danger to lives of occupants.
Wood burning equipment must be vented into a factory
built OR masonary chimney. Chimneys must be built to
Building and Energy Board standards. Do not neglect
cleaning, or deliberately set your chimney on fire to burn
out the soot and creosote. If no damage is done to the
house, there will be damage to the chimney caused by
extreme heat. Not even the best chimneys are designed
for withstand repeated chimney fires.
FACTORY BUILT CHIMNEY MUST BE LABELLED THAT
IT COMPLIES TO UNDERWRITERS LABORATORIES OF
CANADA UCL - S629 - M.
