WOOD STOVE OPERATION & SAFETY - CONTENTS: What to do in the event of a chimney fire How to prevent chimney fires - US CPSC Safety Alert Document # 5047, supplemented & expanded. Metal chimney safety warning. Common causes of fires at woodstoves. Safety warnings about chimney fires & Metal Flues
Here are photos and examples of the wood stove installation and safety details that can help prevent a chimney fire or house fire.
We discuss wood stove installation clearances from combustibles, wood stove draft control or heat output control, wood stove safety checkpoints (including some recommended by the U.S. CPSC) and heating with wood as a means of reducing building or home heating costs.
The article includes wood stove code citations, links to references & researech on using wood stoves, and reports of house or chimney fires related to wood stoves.
Wood Stove, Coal Stove, or Fireplace Insert: Safety Checks
Before using your wood stove, coal stove in the coming or current heating season the US Consumer Product Safety Commission [since 1983 has] strongly urged you,
if you have a [wood stove or coal stove] or fireplace connected to a metal chimney, to check for any damage that may have occurred in the past heating season.
[Click to enlarge any image]
Look for signs of structural failure, such as deformation, cracks, or holes. If it is difficult to examine the chimney, a
local chimney repairman, chimney "sweep", or dealer can help. Have any damage repaired before using the heating device.
Most fires in metal factory-built chimneys occur because of improper installation (such as failure to provide proper fire clearance distances or heat shields or both), improper wood stove use or improper or inadequate maintenance such as permitting an unsafe level of creosote to accumulate in a chimney or flue.
The US CPSC staff has identified the following common causes of wood-stove related fires [supplemented by InspectApedia - Ed] :
Improper chimney installation causing ignition of nearby wood framing.
Structural damage to the chimney caused by burning creosote (a black tar-like substance which builds up inside the
Chimney corrosion resulting in wood framing being exposed to excessive temperatures.
Buckling and collapsing of the inner liner of the chimney. (This can result from too hot a fire, especially in
high-efficiency stoves and in fireplace inserts, or from a creosote fire.)
Many serious fires also occur in masonry chimneys, usually from improper installation or when the tile inner liner and
the surrounding brick or block structure crack and separate. Such cracks may be caused by the ignition of creosote.
Smoke and heat can then escape and ignite material near the chimney.
Even when the heating appliance is properly installed, people with both metal and masonry chimney systems should
frequently check the chimney for creosote deposits, soot build-up or physical damage.
This flue safety check involves only a simple visual
examination, but it should be done as often as twice a month during heavy use.
Signs of or causes of creosote accumulation in a chimney
At wood stoves where creosote is a particular hazard you may suspect creosote build-up if
Green wood: You are burning a lot of green or un-cured or damp wood
Stuck flue damper: You cannot freely rotate the flue damper control
Tap on the metal flue: Thumping or tapping on the metal flue pipe connecting the stove to the chimney makes a dull thump rather than a tinny sound.
Creosote leaks or odors: You see creosote leaking out of stove--pipe joints (which also tells you the flue was assembled upside down and may indicate an amaterur, improper, un-inspected or otherwise unsafe installation).
If you see heavy creosote build-up, suspect a problem, or have had a chimney fire, a qualified chimney repairman or chimney "sweep" should perform a complete safety inspection. They can arrange for any necessary repairs or creosote removal, which must be done before the heating appliance is used again. Details are
at CREOSOTE FIRE HAZARDS.
The US Consumer Product Safety Commission advises owners of metal woodstove or fireplace insert chimneys to:
Be sure that the chimney and stove pipe were installed correctly in accordance with the manufacturers' recommendations
and local building codes. If there is any doubt, a building inspector or fireman can determine whether the system is properly installed.
Have the chimney checked routinely by a chimney "sweep" at least once a year, and more frequently if a stove is heavily
used (for example, if it's used as a primary heat source for the home).
Check air intake and flue damper operation: Check that the chimney flue damper and/or wood stove or coal stove air intake damper can be operated properly. While checking a flue damper you may get a clue that the flue is heavily coated with creosote if you can no longer move the damper freely.
Watch out: if the incoming combustion air cannot be shut down because of leaky woodstove or coal stove gaskets or other damage, the coal stove, woodstove, or pellet stove is unsafe as its burn-rate cannot be regulated.
See DAMPERS & DRAFT REGULATOR TYPES
Always operate your appliance within the manufacturers' recommended temperature limits. Too low a temperature increases
creosote build-up and too high a temperature may lead to a fire. Chimney temperature monitors are available and should
Make sure that your home has working smoke detectors properly installed and located
Make sure that your home has appropriate fire extinguishers, located by the home exit doors, and of an appropriate size and type if you use a fireplace or woodstove.
If you have had a fire or other safety problem with your chimney, please provide this information to the Commission by
calling the Commission's toll-free Hotline 800-638-CPSC.
At FIRE CLEARANCES, WOOD & COAL STOVE FLUES we discuss heat shielding in detail, warning that even relatively low temperatures applied to nearby combustibles can can over time lower the combustion point of nearby combustible materials such as wood framing.
See PYROLYSIS EXPLAINED for those details.
How to Use the Wood Stove Draft Control to Control Heat Output
Watch out: people often leave the woodstove door open for a time after lighting the woodstove fire as a way to boost draft and get the fire going. But if you foreget and leave the door open, at least on some woodstoves and certainly on coal stoves or wood-oil combination boilers and furnaces, the result is a dangerously-overheated heating appliance that can either ruin the appliance (by warping the component parts) or it can set the building or chimney on fire.
Our tenant Stanley Pyrek left the door to our coal stove ajar to get a fire started, then forgot about it. The result was severe overheating of the coal stove, deforming the stove door and other parts so that the stove was no longer usable. This mistake also came close to setting the house on fire. It was an unforegttable experience.
I'm not so sure the wood burning stove shown at left above is a fire-safe installation, but you can plainly see the manual flue damper handle (pointed-to by our blue arrow) in the rusty flue section about 30 inches above the top of the woodstove. When the damper handle's long axis is parallel to the flue the damper is in its fully open position.
Woodstoves also regulate the wood fire and thus stove temperature by adjusting the combustion air intake to the woodstove. Shown just above is a beautiful Jotul woodstove that I (DF) traded to Paul Galow for a fancy wristwatch. The orange arrow points to the woodstove air inlet draft control.
Watch out: if the incoming combustion air cannot be shut down because of leaky wood stove gaskets or other damage the wood stove is unsafe.
In our Norwegian Jotul woodstove photo at above right, Paul has installed air-spaced heat shields of ceramic tile mounted on fireproof board behind the stove and he added a heat shield (the silver contraption) on the side of the stove facing a bed just to slow down the heat in that direction.
That wood-box on the left side of the stove is a bit close in my OPINION but Mr. Galow is not much impressed by my caution.
Our photo at left illustrates a house fire that occurred when a wood burning heater was left running unattended.
Watch out: if the flue damper rusts or becomes damage it may be impossible to slow the chimney draft, resulting in an over-heating stove and possibly a chimney or house fire. Though questionable fire clearances and accumulated creosote may have been factors, just such a runaway wood stove fire and its disastrous results are illustrated
at CHIMNEY FIRE ACTION / PREVENTION (live link is given just below)
Readers wanting to understand how heat as low as 200 degF. can over time lower the combustion point of nearby combustible materials such as wood framing will want to see PYROLYSIS EXPLAINED
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