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Chimney Maintenance

Dirty chimneys can cause chimney fires, which damage structures, destroy homes and injure or kill people. 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. Some are less obvious. 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. The good news is, with proper chimney system care, chimney fires are entirely preventable.

Use Your Fireplace Safely

• Follow the manufacturer's instructions. Carefully follow the manufacturer's instructions for installing and maintaining your chimney or appliance. If you do not have instructions, call the manufacturer. For masonry chimneys, call the builder.
       Note: For all new installations, a Building Permit is required.
• Inspect and clean your chimney regularly. The Ontario Fire Code requires homeowners to maintain the safety of their chimneys and inspect them at least once a year. Your chimney could have a problem you cannot see. If in doubt, consult a Wood Energy Technical Training (WETT) certified chimney sweep.
• Check stovepipes and connections. Ensure screws are located at every joint. Also look for leaching (dark staining or white powder) at every joint. This could be a sign of chimney trouble - consult a WETT certified chimney sweep.
• Check walls for excessive heat. If the wall is very hot, it could be a sign of improper installation of the chimney or stove pipe. Check with a WETT certified chimney sweep.
• Install a rain cap. A rain cap should be installed on top of all metal and masonry chimneys. If you have a spark screen around the chimney cap, inspect it regularly for blockage.
• Watch for smoke coming into the room. This could indicate a blockage in the chimney or a faulty damper control mechanism. Check it out!
• Protect floors and walls from heat and sparks. Keep combustibles safely away from your appliance. Always use a properly fitting screen for your fireplace.
• Regularly check for signs of problems. Your heating appliance, flue pipes and chimney can deteriorate over time. Look for corrosion or rust stains on the outer shell of a metal chimney and check for bulges or corrosion in its liner.

Keep The Fire You Do Want...From Starting One You Don't!

Chimney fires don't have to happen. Here are some ways to avoid them:

• Only use seasoned wood. 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 items 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.

What to do if you have a chimney fire

If you realize a chimney fire is occurring, follow these steps:

1. Get everyone, including yourself, out of the house.
2. Call the fire department.

If you can do so without risk to yourself, these additional steps may help save your home. Remember, however, that you can replace your home, but you can not replace lives:

1. Put a flare type chimney fire extinguisher into the fireplace or wood stove.
2. Close the glass doors on the fireplace.
3. Close the air inlets on the wood stove.
4. Use a garden hose to spray down the roof (not the chimney) so the fire won't spread to the rest of the structure.
5. Monitor the exterior chimney temperature throughout the house for at least two or three hours after the fire is out.

Signs That You've Had a Chimney Fire

If chimney fires can occur without anyone being aware of them and 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 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.

What is Creosote?

Creosote is black or brown residue that sticks to the inner walls of chimneys. 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, there is cause for concern when creosote builds up in sufficient quantities to sustain a long, hot, destructive chimney fire.

Conditions that encourage the build-up of creosote:

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 it is 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 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 to 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 than in a chimney that runs through the centre of a house and exposes only the upper reaches of the flue to the elements.

What is Creosote?

Masonry chimneys:
When chimney fires occur in masonry chimneys, whether the flues are an older, unlined type or are tile lined to meet current safety codes, the high temperatures they burn at (around 2000 F) can melt mortar, crack tiles, cause liners to collapse and damage the outer masonry material. Most often, tiles crack and mortar is displaced, which provides a pathway for flames to reach the combustible wood frame of the house. One chimney fire may not harm a home. A second can burn it down. Enough heat can also conduct through a perfectly sound chimney to ignite nearby combustibles.

Pre-fabricated, factory-built, metal chimneys:
To be installed in most jurisdictions in Canada, factory-built, metal chimneys that are designed to vent wood burning stoves or pre-fabricated metal fireplaces must pass special tests determined by Underwriter's Laboratories of Canada (ULC). Under chimney fire conditions, damage to these systems still may occur, usually in the form of buckled or warped seams and joints on the inner liner. When pre-fabricated, factory-built metal chimneys are damaged by a chimney fire, they should no longer be used and must be replaced