Signs you've had a chimney fire

If you think a chimney fire is happening now

The Chimney Safety Institute of America (CSIA) describes the signs of a dramatic chimney fire: loud cracking and popping, a lot of dense smoke, an intense hot smell, and in some cases flames or dense smoke coming out of the top of the chimney. Some people describe a low rumbling like a freight train or a low-flying airplane.

After the fire department has responded, do not use the fireplace or any appliance connected to that chimney again until it has been evaluated. See What to do after a chimney fire.

Quiet fires that go unnoticed

Not every chimney fire is dramatic. CSIA explains that slow-burning chimney fires are not as visible or loud, often go undetected until a later inspection, and still reach temperatures high enough to damage the chimney structure. CSIA's white paper on chimney fires describes these as burning for long periods with little outward sign, sometimes only a glow.

Quiet fires are a big reason annual inspection matters. A homeowner can use a fireplace for a season after a chimney fire without knowing it happened, while cracked tiles or a damaged liner let heat reach the framing around the chimney.

The evidence a chimney fire leaves

CSIA lists signs that a chimney sweep looks for after a suspected chimney fire. In our own words:

• Puffy or honeycombed creosote. Creosote that has burned swells into a light, porous, sponge-like or popcorn texture, different from the usual flaky or tarry layers.
• Warped metal. A damper, damper frame, metal smoke chamber parts or factory-built chimney sections that are bent, buckled or discolored.
• Cracked or collapsed flue tiles, or tiles with large pieces missing.
• A discolored or distorted cap. A rain cap that looks heat-tinted or warped.
• Heat damage on the roof. Damaged roofing material near the chimney, or a heat-damaged TV antenna attached to it.
• Creosote flakes on the roof or ground. Pieces of burned creosote that were blown out the top.
• Cracks in exterior masonry.
• Smoke escaping through mortar joints of the masonry or tile liners.

Some of these you can see from the ground or the hearth. Others, especially liner damage, need a camera.

What you can safely check yourself

Without climbing a roof or going up the flue, you can look for:

• Black, puffy flakes of creosote on the roof, in gutters, on the ground near the chimney or on the hearth.
• A damper that suddenly sticks, will not close fully or looks bent.
• A cap that looks discolored or out of shape, using binoculars from the ground.
• New cracks in the chimney exterior.
• Smoke appearing anywhere other than the top of the chimney the next time the fireplace is in use. If that happens, put the fire out, stop using it, and arrange an inspection.

Finding one of these is a reason for an inspection. It does not confirm a chimney fire on its own; a warped damper, for example, can have other causes.

What causes chimney fires

Chimney fires happen when creosote inside the flue ignites. CSIA describes creosote as a black or brown residue that can be crusty and flaky, tar-like and sticky, or shiny and hardened, and notes that all forms are highly combustible. Creosote builds faster when air supply is restricted, when unseasoned wood is burned, and when the flue runs cool.

Common triggers include a very hot fire in a flue with heavy deposits, burning paper, cardboard or Christmas tree branches, and long smoldering fires that build deposits followed by a hot fire. A clean, dry flue is far less likely to have a chimney fire. CSIA's message is direct: clean chimneys don't catch fire. See Creosote: stages, risk and removal and How often should a chimney be swept?

Why the damage matters even if the fire went out

A chimney fire can push flue temperatures far above normal for a short time. CSIA's white paper explains that clay tile liners are prone to cracking under that kind of rapid heating, and that the surrounding chimney wall can crack too. A damaged liner may then let heat reach nearby wood framing, or let smoke and carbon monoxide escape, the next time the fireplace or appliance is used.

That is why CSIA advises not using the chimney after a suspected fire until it has been swept and evaluated by a qualified professional. Cracked liners and warped metal components are covered in more detail in What cracked flue tiles mean.

Signs in factory-built fireplaces and stoves

Metal chimneys show fire damage differently from masonry. In a factory-built fireplace or a stove with a metal chimney, look for:

• Chimney pipe sections that are bulged, buckled, discolored or pulled apart at the joints.
• A warped firebox panel or refractory panels that have cracked or fallen.
• Discolored or warped termination caps and chase covers.
• Damaged insulation or scorching in the framed chase around the pipe, where it can be seen.
• Stove connector pipe that is blistered, bluish or warped.

Factory-built chimney systems are tested and listed as a complete system. When parts are heat-damaged, the manufacturer's instructions govern what can be replaced, and in many cases damaged sections must be replaced with the same listed parts. See Factory-built fireplaces: care and limits.

Lowering the risk of another one

Once the chimney has been repaired, the habits that prevent a first chimney fire matter even more:

• Burn only dry, seasoned firewood. The US EPA Burn Wise program advises splitting, covering and drying wood for at least six months.
• Avoid long, smoldering fires with the air turned down, which build creosote.
• Never burn trash, cardboard, wrapping paper or Christmas tree branches.
• Have the chimney inspected every year and swept when deposits build up.
• Keep a working carbon monoxide alarm on every level of the home and outside sleeping areas.

See Burning the right firewood for more.

How a chimney fire is confirmed

1. Document firstPhotograph creosote and damage before cleaning, since sweeping removes some of the evidence. CSIA notes these photos can help with an insurance claim.
2. Sweep the flueRemoving deposits exposes the liner surface.
3. Camera inspectionA video scan of the full flue looks for cracked tiles, open joints, warping and separation.
4. Check the rest of the systemDamper, smoke chamber, cap, crown, roofing, and the attic and framing around the chimney where accessible.
5. Findings and optionsA written explanation with photos of what was found and what repairs, if any, are needed before the system can be used again.

CSIA's description of inspection levels calls for a Level 2 inspection after an operating malfunction or an external event that may have damaged the chimney. See Chimney inspection levels 1, 2 and 3.

Next step

If you see signs of a past chimney fire, stop using the fireplace or appliance. Our chimney fire damage inspection starts with an assessment and photo documentation before cleaning, followed by a camera inspection when the flue allows. You receive the findings with photos before any repair is scheduled. Common repairs after a chimney fire include flue repair, relining or masonry work. Request service to get started.

Questions homeowners ask

Sources

1. CSIA: Preventing Chimney Fires
2. CSIA: After a Chimney Fire
3. CSIA: Chimney Fires: Causes, Effects & Evaluation (white paper)
4. CSIA: The Three Levels of Chimney Inspections
5. US EPA Burn Wise: Burn the Right Wood, the Right Way (tip sheet)
6. US Consumer Product Safety Commission: Carbon Monoxide Information Center

This guide is general information. It can't diagnose a specific chimney; an inspection can.