A sudden roar from your wood burner, loud enough to make you look up from your book, means air is being sucked through a flue that has become a chimney fire. Most homeowners freeze for a second, trying to place the sound. By the time they do, sparks may already be climbing from the pot.
What a Chimney Fire Actually Looks and Sounds Like
The roaring noise draws its power from the draught itself. Burning deposits inside the flue accelerate, pulling more air through the stove, which makes the fire burn hotter and pull harder. The result sounds like a train passing close, or a strong wind trapped inside brickwork. Not every fire announces itself this dramatically. Some burn slowly inside thick layers of creosote, giving subtler warnings that are easy to dismiss.
Watch for sparks or visible flame at the chimney pot, especially after dark. Burning soot or tar may fall into the firebox or onto the hearth. Dense, acrid smoke from the pot, unusual warmth in the chimney breast on upper floors, very warm walls in bedrooms above, or a hearth slab that grows hot to the touch all signal the same problem. Discoloured plaster or materials near the stack confirm heat is escaping where it should not. Some fires do all of this at once. Others smoulder quietly, damaging the structure while the room below feels merely warmer than usual.
The First Minutes Decide Everything
If you hear that roar, or see sparks outside, the sequence matters. Get everyone out of the room and close the door behind you. This slows the spread of smoke and flame if the fire breaks through. Alert anyone else in the house. If you can do so without delay, close the air vents on the wood burner to starve the fire of oxygen. Do not open the stove door to fiddle with controls. Do not carry anything out with you.
Call 999 from outside, clear of the building. Tell the operator you have a chimney fire. Do not climb onto the roof to inspect the pot. Heat, smoke, and the structural weakening caused by the fire itself make this lethal. Do not pour water down the chimney or onto the fire. Water hitting temperatures above 1000°C converts instantly to steam, expanding roughly 1700 times in volume. The resulting pressure can shatter a flue liner, damage mortar, and force fire into the house structure through gaps that did not exist thirty seconds before.
Wait for the Fire and Rescue Service at a safe distance. They carry specialist chimney fire extinguishers that smother the flue with inert material and know how to check for extension into roof spaces without adding risk.
Why the Danger Outlasts the Flames
The fire service will make the property safe, but safe to enter is not safe to light. Chimney fires exceed 1100°C, far beyond what domestic flues are built to withstand repeatedly. That heat cracks clay liners, warps or melts stainless steel ones, and opens mortar joints between bricks. Spalling, where the face of a brick flakes off from thermal shock, weakens the stack. None of this is reliably visible from the hearth.
Heat transfers sideways through masonry to timber joists, rafters, and insulation. These materials can sit at ignition temperature for hours, then flare after everyone has gone to bed. Embers lodged in cracks or voids smoulder undetected. The chimney that looks intact from below may be a lattice of passages feeding heat into the building.
A damaged flue also loses its ability to contain combustion gases. Carbon monoxide, produced by any solid fuel appliance, can leak through cracks into bedrooms or living spaces. It has no smell, no colour, and kills efficiently.
What Must Happen Before You Burn Again
The chimney cannot be swept and pronounced ready. It needs a sequence of checks, each building on the last.
A certified chimney sweep, preferably a member of NACS or the Guild of Master Sweeps, must clean the flue thoroughly. Soot and creosote residue obscure damage and can reignite if left. Once clean, a CCTV camera inspection examines the full length of the flue for cracks, joint failures, liner deformation, or spalling that a brush cannot reach.
A smoke leakage test, conducted to BS EN 15287-1, checks whether the flue is gas-tight. A flue that draws well can still leak into adjacent flues, roof spaces, or upstairs rooms under pressure. The test finds pathways that visual inspection misses.
A HETAS-registered installer or qualified chimney engineer should assess the stack, breast, and hearth for structural compromise. If the liner is damaged, replacement with a flexible stainless steel liner to BS EN 1856-2 is usually the fix. Clay or concrete liners that have cracked generally cannot be repaired in situ.
You need a written condition assessment confirming the chimney is fit for reuse. Keep this for your insurance company and your own records. Do not rely on verbal assurance, and do not accept a sweep’s word that it “looks all right” without the camera survey and smoke test.
The chimney that roared has told you something important about its condition. What you do in the hour after, and the weeks that follow, determines whether that warning becomes a story you tell, or a story the fire service tells about your house.