What to do during and after a chimney fire

What to do if a chimney fire starts: get out, then call 911

If you hear roaring in the chimney, see flames or sparks coming from the top, or smoke is pouring into the room, take everyone out of the house, then call 911 from the yard or a neighbor's phone. Tell the dispatcher it is a chimney fire, so the crew knows to check the roof, the attic and the walls beside the chimney.

Do not climb onto the roof and do not stay inside to fight it. Pouring water down a hot flue turns to steam at once, and the sudden cooling can crack flue tiles that were sound a minute earlier. A garden hose on the roof is a fall risk and does little to a fire burning inside the flue. Once outside, keep children and pets back from the house and watch for sparks settling on the roof or the lawn, and point them out to the firefighters.

Signs of a chimney fire in progress

A fast, hot chimney fire is hard to miss. The sound is a loud cracking and popping that builds into a low roar, which people compare to a passing train. Dense smoke can push out of the fireplace opening, flames or glowing debris can shoot from the top of the stack, and the room fills with a hot, sharp smell unlike an ordinary wood fire.

A slow-burning chimney fire can be much quieter. It may smolder in the flue without drama, starved of air, and still reach temperatures that crack tile and scorch framing. So a fire that seemed to go out quietly still needs the same follow-up as a loud one. If the walls beside the chimney feel hot to the touch, or you smell smoke in a room upstairs that has no fireplace, treat it as a fire and get out.

Where the fuel comes from

Wood smoke carries water vapor, unburned gases and fine particles up the flue. As the smoke cools, part of it condenses on the flue walls as creosote, a deposit that ranges from light, flaky soot to a hard, shiny glaze. Every form of it burns, and a thick enough layer is fuel waiting for a hot fire underneath it to ignite it.

Some conditions build creosote faster than others. Wet or unseasoned wood burns cool and smoky. Fires that smolder with the air turned down send heavy smoke up a cool flue. An oversized flue, or an exterior chimney that stays cold, lets the smoke cool early. Burning trash, cardboard or wrapping paper adds its own residue and can send burning pieces up the flue that light the deposit from below.

Signs of a fire you did not notice

A chimney fire that nobody heard can still be found later, during a sweep or an inspection. These are the clues we look for, and some of them you can check yourself from the yard or the firebox.

• Creosote that has puffed up into a honeycomb or popcorn texture, which is how the deposit looks after it has burned
• A warped damper plate or frame, or a damper that no longer seats
• Flue tiles with cracks, open joints or missing pieces, sometimes with tile fragments in the firebox
• A metal cap that is discolored or distorted, or a spark screen with melted or burned-through mesh
• Flakes or chunks of burned creosote on the roof or on the ground below the chimney
• New cracks in the outside masonry, or smoke seeping from joints when the fireplace is in use
• Scorched wood or heat-darkened insulation in the attic beside the chimney

Why the next fire waits for an inspection

The heat of a chimney fire goes well past what a flue is built to handle. Clay tiles crack from the thermal shock, mortar joints between tiles open, and on a factory-built system the metal chimney sections can warp or separate. Any of these can leave a gap that lets heat and embers reach the wood framing around the chimney on the next fire, which is how a flue fire becomes a house fire weeks later.

NFPA 211, the national standard for chimneys, fireplaces and vents, calls for a more thorough examination of a chimney after an event likely to have damaged it, and a chimney fire is the clearest case. That examination covers the flue from end to end, the smoke chamber and damper, the firebox, the crown, cap and flashing, and the framing and clearances that can be reached in the attic. For a factory-built fireplace, the maker's instructions say which parts have to be checked or replaced after a fire, and repairs use listed parts that match the unit.

Follow any instructions the fire department leaves with you, since they may have checked walls and the attic for heat before leaving. Their job is putting the fire out, not judging whether the flue is fit for another fire. Until the inspection is done and any repairs are made, keep the fireplace, the insert or the stove out of service.

What repairs can follow

The inspection's findings decide the work. The estimate itemizes the work, with safety items marked apart from those that can be scheduled later. Remaining creosote is swept out, and glazed deposits that do not brush off get a separate removal process. Cracked flue tile is either repaired where the damage is limited or, where tiles are broken along the run, the flue is relined with a stainless steel liner listed to UL 1777 and sized to the appliance.

A warped damper is replaced, either with a new throat damper or with a top-sealing damper. A burned cap or screen is replaced with one sized to the flue. Cracked outside masonry is repointed or rebuilt, and any scorched framing found in the attic is work for a carpenter or general contractor, which the estimate names separately. If the fire department filed a report, keep a copy with the estimate and the final invoice.

Keeping it from happening again

The habits that prevent a chimney fire are the same ones that keep a fireplace efficient. Burn wood that has been split and seasoned, which EPA Burn Wise describes as at least six months of drying and a moisture meter reading below 20. Build small, hot fires and do not let them smolder for hours with the air shut down. Keep trash, cardboard and wrapping paper out of the firebox.

Have the chimney inspected once a year, the interval NFPA 211 sets, and swept when the inspection finds deposits building up. Keep a cap with an intact spark screen on the flue. If you use the fireplace heavily, or you notice more smoke or a darker, tarry deposit at the damper, ask for a check sooner rather than waiting for the yearly visit.