Chimney fire: signs, what to do and what comes after

What a chimney fire is

Burning wood produces smoke that contains unburned tar and vapour. As the smoke cools in the flue, these condense on the walls as creosote: flaky, tarry or hard and shiny. Creosote burns. When enough has built up and a hot fire or a spark sets it off, the deposit itself catches fire inside the chimney.

Temperatures in a chimney fire can be high enough to crack clay flue tiles, warp metal liners and ignite the wooden framing next to the chimney.

Signs it is happening

Some chimney fires are dramatic:

• A loud roaring, rumbling or sound like a freight train or a low-flying aircraft
• Loud cracking and popping
• Flames or sparks shooting from the top of the chimney
• Dense smoke from the chimney or back into the room
• An intense hot smell
• The stove pipe or chimney glowing or shaking

Others are slow and quiet. They burn with limited air, go unnoticed and are discovered only at the next inspection. These can do just as much damage.

What to do

1. Get everyone out of the house.
2. Call 911 from outside. Call even if the fire seems to go out.
3. If it is safe and takes only a moment, close the air inlets and damper on a wood stove, or close the glass doors on a fireplace, to starve the fire of air. Do not put yourself at risk.
4. Do not pour water into the stove or fireplace. Steam can cause burns, and the sudden cooling can crack the flue and firebox.
5. Wait for the fire department to confirm it is out and to check the walls, attic and roof for spread.

Afterwards: do not light it again

A chimney that has had a fire may no longer contain the next one. Before any further use, have it inspected by a certified professional. In Ontario, look for a technician or sweep certified by Wood Energy Technology Transfer (WETT). The inspection should include the inside of the flue for its full height, usually with a camera.

Signs that a chimney fire has occurred:

• Puffy, honeycombed or grey, ash-like creosote
• Cracked or collapsed flue tiles, or pieces of tile in the firebox
• Warped metal: the damper, the stove pipe, the liner or the chimney cap
• A discoloured or distorted rain cap
• Cracks in the exterior masonry, or smoke stains at mortar joints
• Scorched roofing near the chimney
• Smoke escaping into the attic or through walls

Typical repairs

• Relining. A damaged clay liner is commonly replaced with an insulated stainless steel liner sized for the appliance.
• Replacing a factory-built metal chimney that has been overheated. These are generally not repairable once warped.
• Masonry repair to the crown, bricks and mortar.
• Replacing stove pipe, dampers and caps.
• Repairs to framing and roofing if heat or fire reached them.

Work must restore the clearances to combustible materials that the codes and the manufacturer require.

Smoke and heat damage in the house

Even when the fire stays in the flue, the house can be affected.

• Smoke and soot pushed back into the room coat walls, ceilings and furnishings.
• Heat passing through cracks in the liner can char framing inside walls and the attic without visible flames. This hidden charring is why the fire department opens things up to look.
• Water from firefighting soaks the area round the chimney.
• Odour lingers in soft furnishings and the heating system.

Cleaning follows the usual order for soot: dry removal with HEPA vacuums and dry cleaning sponges first, then wet cleaning, then sealing and repainting stained surfaces. Do not wipe soot with a wet cloth. Switch off the furnace fan until the area has been cleaned so that soot is not carried round the house.

Carbon monoxide

A damaged flue can leak combustion gases into the house. Ontario law requires carbon monoxide alarms in homes with fuel-burning appliances, fireplaces or attached garages. Check that yours work. If an alarm sounds, leave and call 911.

Insurance

Fire and smoke damage from a chimney fire are generally covered under standard home policies. Two points to know:

• Your insurer may ask about the installation and maintenance of the appliance. Many insurers ask for a WETT inspection report for wood-burning appliances when a policy is taken out.
• Deterioration from wear and age is not covered. A chimney fire is a sudden event, but an adjuster will distinguish its damage from long-standing decay.

Tell your insurer or broker about any wood-burning appliance when you install one.

Preventing chimney fires

• Have the chimney inspected and swept at least once a year, and more often with heavy use. Ontario’s Fire Code requires chimneys and flues to be inspected annually and cleaned as often as necessary to keep them free of dangerous accumulations.
• Burn dry, seasoned hardwood. Wet wood makes cool, smoky fires that lay down creosote. Wood should be split and dried for a season or more.
• Burn hot, bright fires instead of letting the stove smoulder with the air shut down.
• Do not burn rubbish, cardboard, painted or treated wood, or glossy paper.
• Use a properly sized, insulated liner. An oversized or cold flue collects creosote quickly.
• Fit a chimney cap to keep out rain, animals and nests.
• Keep a working smoke alarm on every storey and outside sleeping areas.
• Have an extinguisher nearby and know how to use it.

Buying a house with a fireplace or wood stove

Ask for a WETT inspection before relying on it. Evidence of a past chimney fire, or an unlined or damaged flue, is common in older homes and is not always visible from the room.

More: fire damage restoration and smoke odour removal.