Possible signs of a chimney fire include a loud roaring or rumbling sound, flames or sparks from the chimney pot, unusual heat, a strong burning smell, smoke entering the property or a sudden change in chimney draw. If you suspect a chimney fire, get everyone out and call 999.

Allowing a wood fire to smoulder at a low temperature, or burning wood with too much moisture, can produce more smoke and encourage tar and creosote to build up inside the chimney. Because these deposits are combustible, heavy buildup increases the risk of a chimney fire.

There is no single symptom that proves you are burning too cool or that creosote is building up. However, repeated blackening of the stove glass, excessive smoke, poor fire performance, tar-like deposits or changes in chimney draw are all reasons to look more closely at the fuel, appliance and chimney.

Do not use the chimney again after a suspected chimney fire until it has been appropriately assessed.

How Do Low-Temperature Burning and Wet Wood Increase Chimney Fire Risk?

Wood combustion produces smoke containing gases, vapours and particles. When combustion is incomplete or the smoke cools as it travels through the flue, some of that material can condense on the chimney surface as tar and creosote.

Two common contributors are:

• Prolonged low-temperature burning: restricting the air supply excessively or allowing a fire to smoulder can produce more smoke and encourage deposits to form.
• Burning wood that is too wet: energy is used evaporating water rather than supporting effective combustion, which can lower the fire temperature and increase smoke.

Other factors can also contribute, including the appliance, ventilation, chimney size and arrangement, chimney temperature, amount of use and sweeping frequency. Heavy deposits do not automatically mean that one particular burning mistake is responsible.

What Are the Signs a Wood Fire Is Burning Inefficiently?

Possible signs that warrant attention include:

• Stove glass becoming heavily blackened soon after cleaning
• A fire that repeatedly struggles to establish or stay alight
• More smoke than you would normally expect once the fire is established
• A noticeable deterioration in chimney draw
• Smoke entering the room or puffing back when the appliance door is opened
• Persistent smoky or tar-like smells
• A change in the way the appliance normally behaves

These symptoms are not a diagnosis. Poor draw or smoke entering the room can also be caused by an obstruction, ventilation problem, appliance issue or unsuitable chimney arrangement.

What Are the Signs of Tar or Creosote Buildup?

Creosote and tar can appear in different forms. Signs can include black or brown deposits, sticky tar-like material, hard shiny deposits, dark flakes falling into the fireplace or material that remains after an ordinary chimney sweep.

A strong smoky or tar-like smell can also occur, although chimney smells can have several other causes. For a detailed explanation, read our guide to creosote and tar in chimneys.

What Are the Signs of a Chimney Fire?

A chimney fire can be obvious, but it is not always easy for the householder to identify exactly what is happening inside the flue. Possible signs include:

• A loud roaring or rumbling sound from the chimney
• Flames or sparks emerging from the chimney pot
• An unusual increase in heat around the chimney or appliance
• A strong burning smell
• Smoke entering the property
• Material falling into the fireplace or appliance
• A sudden or unusual change in the way the fire is drawing

Do not wait for several symptoms to appear before taking a suspected chimney fire seriously.

What Should You Do If You Suspect a Chimney Fire?

If you believe there may be a fire in the chimney, treat it as an emergency.

1. Get everyone out of the property.
2. Call 999 and ask for the fire and rescue service.
3. Do not put yourself at risk trying to investigate the chimney.
4. Do not deliberately add water to the chimney or light another fire to test it.
5. Do not return to the property until the emergency services say it is safe.

What Should You Do After a Chimney Fire?

Do not use the chimney again until it has been appropriately assessed.

A chimney fire can expose liners, mortar joints and other chimney components to intense heat. The extent of any damage cannot be established simply from the fact that the fire has gone out or that no damage is visible in the room.

After a chimney fire, the chimney should be swept and a CCTV chimney survey carried out before the chimney is used again. The survey allows the inside of the flue to be inspected for damage or defects that may have resulted from the fire.

How Can You Reduce the Risk of a Chimney Fire?

Reducing combustible deposits and addressing the conditions that create them are both important.

• Use suitable fuel and, when burning wood, use properly dried wood appropriate for the appliance.
• Follow the appliance manufacturer’s operating instructions rather than routinely restricting the air supply to keep a fire smouldering.
• Do not block ventilation provided for the appliance.
• Have the chimney swept at a frequency appropriate to the fuel, appliance and amount of use.
• Investigate repeated tar or creosote buildup rather than simply removing it again and again.
• Have changes in draw, smoke entering the room or unusual appliance performance investigated.

Our separate chimney fire prevention guide covers burning technique and maintenance in more detail.

Frequently Asked Questions

Does black stove glass mean I have creosote in my chimney?

No. Rapidly blackening stove glass can indicate poor combustion, wet fuel or another appliance issue, but it does not prove that dangerous creosote is present in the chimney. If it happens repeatedly, review the fuel and appliance operation and arrange professional advice if the cause is unclear.

Can wet wood cause creosote buildup?

Wet wood can contribute to creosote and tar formation because energy is used evaporating moisture, combustion can be cooler and more smoke can be produced. Creosote buildup can have several contributing causes, so the fuel should be considered alongside the appliance and chimney arrangement.

Can burning a stove too slowly cause creosote?

Prolonged low-temperature or smouldering combustion can encourage creosote and tar deposits to form. Operate the appliance in accordance with the manufacturer’s instructions rather than excessively restricting the air supply simply to make the fuel last longer.

What are the first signs of a chimney fire?

Possible signs include roaring or rumbling from the chimney, an unusual increase in heat, sparks or flames from the chimney pot, a strong burning smell, smoke entering the property or a sudden change in chimney draw. If you suspect a chimney fire, leave the property and call 999.

Can a chimney fire happen without you knowing?

Not every chimney fire presents in the same way, and a householder may not always recognise what has happened inside the flue. If there is reason to suspect a chimney fire, do not use the chimney again until it has been appropriately assessed.

Do I need a CCTV survey after a chimney fire?

Yes. After a chimney fire, we require the chimney to be swept and a CCTV chimney survey carried out before it is used again. This allows the inside of the flue to be inspected for damage or defects caused by the fire.

Will a normal chimney sweep remove creosote?

Ordinary sweeping can remove soot and many loose or brittle deposits. Hardened, sticky, glazed or firmly bonded tar and creosote may require specialist treatment. Our tar and creosote removal service explains the treatment we use for deposits that cannot be removed by ordinary sweeping.