Blog By: FireRein Staff
with files from https://www.csia.org/chimneyfires.html
Chimney Fire Hazards
The Majority of Chimney Fires Go Undetected Slow-burning chimney fires don’t get enough air or have fuel to be dramatic or visible
and they often go undetected until a later chimney inspection, but, the temperatures
they reach are very high and can cause as much damage to the chimney structure –
and nearby combustible parts of the house – as their more spectacular cousins.
Creosote & Chimney Fires: What You Must Know Fireplaces and wood stoves are designed to safely contain wood-fuel fires, while
providing heat for a home. The chimneys that serve them have the job of expelling the
by-products of combustion – the substances produced when wood burns. These include smoke, water vapor, gases, unburned wood particles, hydrocarbon, tar fog and assorted minerals. As these substances exit the fireplace or wood stove, and flow up into the relatively cooler chimney, condensation occurs. The resulting residue that sticks to the
inner walls of the chimney is called creosote. Creosote is a black or brown residue that can be crusty and flaky…tar-like, drippy
and sticky…or shiny and hardened. All forms are highly combustible. If it builds up
in sufficient quantities – and the internal flue temperature is high enough – the result
could be a chimney fire.
Conditions that encourage the buildup of creosote:
· restricted air supply
· unseasoned wood
· cooler than normal chimney temperatures
Air supply may be restricted by closing the glass doors, by failing to open the damper
wide enough, and the lack of sufficient make-up air to move heated smoke up the chimney rapidly (the longer the smoke’s “residence time” in the flue, the more likely is it that creosote will form). A wood stove’s air supply can be limited by closing down the stove damper or air inlets too soon or too much. Burning unseasoned wood – because so much energy is used initially just to drive off the water trapped in the cells of the logs– keeps the resulting smoke cooler, than if seasoned wood is used. In the case of wood stoves, overloading the firebox with wood in an attempt to get a longer burn time also contributes to creosote buildup.
The Effect of a Chimney Fire on Your Chimney Masonry Chimneys When a chimney fire occurs in a masonry chimney – whether the flue is an older, unlined type or tile lined to meet current safety codes – the high temperatures at which they
burn (around 2000°F) can “melt mortar, crack tiles, cause liners to collapse and damage the outer masonry material”. Most often, thermal shock occurs and tiles crack and mortar
is displaced, which provides a pathway for flames to reach the combustible wood frame
of the house. This event is extremely dangerous, call 911 immediately. Prefabricated, factory-built, metal chimneys To be installed in most jurisdictions in the United States, factory built, metal chimneys
that are designed to vent wood burning stoves or prefabricated metal fireplaces must pass special tests. Most tests require the chimney to withstand flue temperatures up to 2100°F – without sustaining damage. Under chimney fire conditions, damage to these systems still may occur. When prefabricated, factory-built metal chimneys are damaged by a chimney fire, they should no longer be used and must be replaced. Special Effects on Wood Stoves Wood stoves are made to contain hot fires. The connector pipes that run from the stove
to the chimney are another matter. They cannot withstand the high temperatures produced during a chimney fire and can warp, buckle and even separate from the vibrations created by air turbulence during a fire. If damaged by a chimney fire, they must be replaced. Nine Signs that You’ve Had a Chimney Fire Since a chimney, damaged by a chimney fire, can endanger a home and its’ occupants
and a chimney fire can occur without anyone being aware of them it’s important to have your chimney regularly inspected by a CSIA Certified Chimney Sweep. Here are the signs that a professional chimney sweep looks for:
· “Puffy” or “honey combed” creosote
· Warped metal of the damper, metal smoke chamber connector pipe
or factory-built metal chimney
· Cracked or collapsed flue tiles, or tiles with large chunks missing
· Discolored and/or distorted rain cap
· Heat-damaged TV antenna attached to the chimney
· Creosote flakes and pieces found on the roof or ground
· Roofing material damaged from hot creosote
· Cracks in exterior masonry
· Evidence of smoke escaping through mortar joints of masonry or tile liners
If you think a chimney fire has occurred, call a CSIA Certified Chimney Sweep for
a professional evaluation. If your suspicions are confirmed, a certified sweep will be
able to make recommendations about how to bring the system back into compliance
with safety standards. Depending on the situation, you might need a few flue tiles
replaced, a new liner system installed or an entire chimney rebuilt. Each situation is
unique and will dictate its own solution.
Proper Maintenance Clean chimneys don’t catch fire. Make sure a CSIA Certified Chimney Sweep®
inspects your solid fuel venting system annually, and sweeps and repairs it
whenever needed. Your sweep may have other maintenance recommendations
depending on how you use your fireplace or stove. CSIA recommends that you
call on CSIA Certified Chimney Sweeps®, since they are regularly tested on their understanding of the complexities of chimney and venting systems.
A Chimney Is An Extension Of Your Heating Appliance “NOT” An Incinerator
Please keep in mind that over the holidays it is easy to accumulate such things as cardboard, gift wrapping, and packing materials as well as paper plates and plastic
cutlery. It is an easy temptation to just send it up the chimney… however it is not recommended to burn boxes and wrapping paper. Especially the wrapping paper;
it burns a little differently.
One of the by-products of any kind of burning is the aforementioned creosote which starts to coat the inside of your chimney, and when you get a coating of creosote in your chimney, then you have a chance of having a chimney fire. Fire officials advise people to burn clean dry and seasoned wood only. One of the secrets of having a good fire is burning clean material, making sure you get the fire up to a good heat so it actually starts to burn off
the creosote or doesn’t allow the creosote to accumulate. Then, you’ll have it at a good operating temperature.
If you follow these signs and helpful tips you will most certainly ensure safe operations during your heating season. This may also get you onto the “Nice List”, which never
hurts. Perhaps this will then guarantee a visit from the Jolly Old Elf himself.
Happy Holidays from all of us at FireRein Inc.
By the 16th century, it was tradition for Dutch children to leave their shoes on the hearth the night before the Feast of St. Nicholas. They would then wake to find the shoes filled with candy and presents, that they believed the saint had lowered down the chimney.