A chimney fire happens when creosote — the flammable residue lining a wood-burning flue — ignites. It can burn at over 1,000 degrees Celsius, crack liners, and spread into your roof or walls. If you suspect one right now: get everyone out, call 000, and do not use the fireplace again until it has been professionally inspected. Even a fire that appears to go out can leave the chimney dangerously damaged.
This guide explains what causes chimney fires, how to recognise one, exactly what to do if you have one, and the straightforward habits that prevent them. If you are dealing with an emergency now, skip straight to the response section — otherwise read on, because prevention is almost entirely within your control.
What Causes Chimney Fires
Nearly every chimney fire has the same root cause: creosote. Understanding the chain of events is the key to preventing it.
Creosote forms when wood smoke cools and condenses on the flue walls, leaving a flammable tar-like deposit. Over time it accumulates — first as light soot, then hard flakes, then a glassy glaze in its most dangerous form. When the layer is thick enough and the flue gets hot enough — typically from a hot, fast fire lit after a period of slow smouldering burns — the creosote ignites.
Three habits drive dangerous buildup: burning unseasoned or wet wood, which smokes heavily and deposits creosote several times faster; running the fire choked down low for long overnight burns, which keeps the flue cool and maximises condensation; and skipping regular cleaning, which lets creosote accumulate unchecked. In Melbourne, where wood heaters run hard all winter and firewood is often sold under-seasoned, all three are common. The good news: all three are also entirely fixable.
How to Recognise a Chimney Fire
Chimney fires come in two forms, and knowing both is important because one is easy to miss.
A fast, dramatic chimney fire is unmistakable: a loud roaring or crackling sound like a freight train or jet, dense smoke and sparks shooting from the chimney top, an intense hot smell, and sometimes a vibrating or rumbling sensation through the structure. If you experience this, it is an emergency.
A slow chimney fire is far more insidious. It can burn quietly at lower intensity, doing serious structural damage — cracking the liner, weakening masonry — without the dramatic signs, and the homeowner may never know it happened. The damage then sits hidden until the next fire finds a crack. This is exactly why any suspected fire, however minor, warrants a professional inspection, and why regular inspections catch the evidence of past slow fires.
What to Do During a Chimney Fire
If you suspect an active chimney fire, act immediately and in this order. Your safety comes first, always.
1. Get everyone out. Evacuate all people and pets from the house immediately. 2. Call 000 and ask for the fire brigade — do this even if you think the fire is small or going out, because hidden spread into the roof is the real danger. 3. If you can do so safely, close the appliance's air supply and damper to starve the fire of oxygen, and close the wood heater door — but never put yourself at risk to do this. 4. Do not use water on a wood heater fire. 5. Get out and stay out until the fire brigade confirms it is safe.
Afterward, do not use the fireplace again until it has been professionally inspected, no matter how minor the fire seemed. A chimney fire can crack the liner and damage the structure in ways that are invisible from inside the room but make the next fire genuinely dangerous — see chimney liner types and lifespan. Your insurer will also typically require a professional inspection — see chimney and fireplace insurance claims.
How to Prevent Chimney Fires
This is the reassuring part: chimney fires are almost entirely preventable, and the steps are simple and inexpensive.
Burn properly seasoned wood. Dry hardwood, seasoned at least 12 months to under 20% moisture, burns hot and clean and deposits far less creosote. See the best firewood for Melbourne. Run hot, bright fires rather than choking the heater down for long slow burns — higher flue temperatures stop creosote condensing. Our guide on how to light a fire correctly covers the technique. Clean and inspect annually, before the Melbourne winter, and twice a year for heavy use — this removes creosote before it can build to a dangerous level. See how often you should clean your chimney.
Do those three things and your flue stays at the harmless early stage of creosote, where a chimney fire simply has no fuel to take hold. Annual professional cleaning is the single most effective preventive measure available.