Fire Prevention Week is October 8-14, 2023
This coming weekend is Thanksgiving. While enjoying your wood-burning fire, remember to take precautions. In honour of Fire Prevention Week, we provide you with the following article. As always, stay safe.
This article was provided as a public information piece by the WETT Communications Committee for members to share. We recommend that you share it with your networks/client base as a marketing tool for your business.
Chimney Fire Facts
As you snuggle in front of a cozy fire or bask in the warmth of your wood stove, you are taking part in a ritual of comfort and enjoyment handed down through the centuries. The last thing you are likely to be thinking about is the condition of your chimney. However, if you don't give some thought to it before you light those winter fires, your enjoyment may be very short-lived. Why? Dirty chimneys can cause chimney fires, which damage structures, destroy homes and injure or kill people.
Fireplaces and wood stoves are designed to safely contain wood-fuelled fires, while providing heat for a home. The chimneys that serve them have the job of expelling the by-products of combustion — the substances given off when wood burns.
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 black or brown in appearance. It can be crusty and flaky; tar-like, drippy and sticky; or shiny and hardened. Often, all forms will occur in one chimney system.
Whatever form it takes, creosote is highly combustible. If it builds up in sufficient quantities — and catches fire inside the chimney flue — the result will be a chimney fire. Although any amount of creosote can burn, sweeps are concerned when creosote builds up in sufficient quantities to sustain a long, hot, destructive chimney fire.
Certain conditions encourage the build-up of creosote: restricted air supply, unseasoned wood and cooler-than- normal chimney temperatures are all factors that can accelerate the build-up of creosote on chimney flue walls.
Air supply
The air supply on fireplaces may be restricted by closed glass doors or by failure to open the damper wide enough 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 and too much, and by improperly using the stovepipe damper to restrict air movement.
Burning unseasoned firewood
Because so much energy is used initially just to drive off the water trapped in the cells of the logs, burning green wood keeps the resulting smoke cooler as it moves through the system than if dried, seasoned wood is used.
Cool flue temperatures
In the case of wood stoves, fully-packed loads of wood (that give large cool fires and eight- or 10-hour burn times) contribute to creosote build-up. Condensation of the unburned by-products of combustion also occurs more rapidly in an exterior chimney, for example, than in a chimney that runs through the centre of a house and exposes only the upper reaches of the flue to the elements.
Failing to maintain your woodstove or fireplace properly can lead to a chimney fire. Chimney fires occur when creosote deposits on the inner walls of the chimney ignite. A fire hazard exists if 1/4 inch of creosote (or more) coats the inner walls of the chimney.
Chimney fires can burn explosively — noisy and dramatic enough to be detected by neighbours or passers-by. Flames or dense smoke may shoot from the top of the chimney. Homeowners report being startled by a low rumbling sound that reminds them of a freight train or a low flying airplane. However, those are only the chimney fires you know about. Slow-burning chimney fires don’t get enough air or have enough fuel to be as dramatic or visible. 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. With proper chimney system care, chimney fires are entirely preventable.
WAYS TO KEEP THE FIRE YOU WANT... FROM STARTING ONE YOU DON'T!
Chimney fires may even occur in clean, intact, properly installed chimneys. Have a WETT-certified chimney sweep clean and inspect your appliance at least once a year. More frequent cleanings may be required, based on the type of wood burned, the type of appliance and the frequency of use. In general, an older, uncertified wood stove, or any appliance that is used frequently, will require more than one cleaning per year.
Make sure a WETT-certified chimney sweep inspects your solid-fuel-venting system annually, and cleans and repairs it whenever needed.
Chemical cleaners and/or log products should not be used for maintenance in a wood-burning appliance. Do not depend on them to clean your chimney. A chimney requires professional sweeping on a regular basis; regular chimney inspections are always recommended. The Creosote Sweeping Log (CSL) will not tell you if your chimney is blocked or has any kind of structural damage. The Creosote Sweeping Log does not take the place of inspection and professional cleaning.
Your sweep may have other maintenance recommendations depending on how you use your fireplace or stove. WETT recommends that you call on certified chimney sweeps, since they are regularly tested on their understanding of the complexities of chimney and venting systems.
Chimney fires don’t have to happen. Here are some ways to avoid them:
Use seasoned woods only (dryness is more important than hard wood versus soft wood considerations)
Build smaller, hotter fires that burn more completely and produce less smoke
Never burn cardboard boxes, wrapping paper, trash or Christmas trees; these can spark a chimney fire
Install stovepipe thermometers to help monitor flue temperatures where wood stoves are in use, so you can adjust burning practices as needed
Have the chimney inspected and cleaned on a regular basis
Detection
The first indication of a chimney fire is usually the noise — a roaring sound that grows louder as the fire’s intensity increases. Clouds of black smoke and sparks will be seen exiting the top of the chimney; in severe fires, flames can extend several feet about the chimney.
Action
In case of a chimney fire, follow these steps:
Call the fire department immediately.
If able to, close the appliance’s dampers and/or the primary air inlet controls, limiting the fire’s air supply and reducing its intensity. If there is a barometric damper in the chimney connector, plug or close the opening in the barometric damper.
Alert and assist everyone in the house to evacuate, including you.
Closely monitor all combustible surfaces near the chimney. During severe chimney fires, these surfaces can become hot enough to ignite.
After a chimney fire, have the chimney inspected by a WETT-certified chimney technician/sweep. Contact your insurance carrier.
DO NOT USE THE CHIMNEY UNTIL IT HAS BEEN INSPECTED by a WETT-certified technician/sweep. The excessive heat produced by a chimney fire can crack chimney walls, damage chimney liners, and damage some types of factory- built chimneys. If not repaired, these damages create a greater possibility for any subsequent chimney fire to spread beyond the confines of the flue to the house.
Signs that You've Had a Chimney Fire
Since chimney fires can occur without anyone being aware of them ... and since damage from such fires can endanger a home and its occupants, how do you tell if you've experienced a chimney fire?
Here are the signs a professional chimney sweep looks for:
“puffy” creosote, with rainbow-coloured streaks, that has expanded beyond creosote’s normal form
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
discoloured and distorted rain cap
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 WETT-certified technician/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 relining system installed or an entire chimney rebuilt. Each situation is unique and will dictate its own solution.