Chimney fires arise when accumulations within a flue spontaneously ignite. Such deposits often consist of tar and creosote, which solidify as flue gases cool, or can result from detritus introduced by nesting avians.
The Phenomenon of a Chimney Fire
Flammable deposits within the flue can be kindled by errant sparks or embers ascending the chimney, or through the operation of an appliance at excessively high temperatures. Once these deposits ignite, the ensuing combustion can propel sparks and flames out of the chimney’s apex.
A chimney inferno can establish itself with alarming rapidity. Sparks may disperse from the chimney’s summit or through fissures in the flue, potentially igniting the roof, structural timbers, or other parts of the dwelling. Adjacent structures and vegetation are also susceptible to ignition.
Indicators of a Chimney Fire
Be vigilant for the following signs that may indicate a chimney or flue fire:
- Externally: Emission of sparks and flames from the chimney pot’s apex.
- Auditory: A resonant, roaring sound emanating from within the chimney or flue.
- Physical: Noticeable vibrations in the stove, flue pipe, or connector.
- Visual: A luminous, shimmering, and intensely hot flue pipe or stove connector.
- Olfactory: The scent of smoke in proximal rooms or attic spaces.
- Thermal: Detectable heat in the chimney breast where the flue pipe traverses, noticeable either in the same room or the room above.
It is feasible for a chimney fire to occur without manifest visual signs, yet still inflict considerable damage.
Factors Elevating Chimney Fire Risks
Several elements can augment the probability of a chimney fire:
- Combustion of inappropriate materials, especially wet, unseasoned wood.
- Utilisation of a poorly installed wood-burning stove.
- Operation of an incorrectly dimensioned open fire.
- Irregular and ineffective chimney sweeping.
- Prolonged burning or smouldering of wood at low temperatures in a wood-burning stove.
Among these, the smouldering of wood or other fuels at low temperatures overnight in a wood-burning stove is particularly hazardous. The diminished oxygen supply and heat result in incomplete combustion. The resultant unburnt substances, such as tar, creosote, and paraffin, adhere to the flue liner, posing a significant ignition risk. Tar adhering to the flue’s interior is notoriously difficult to eradicate, akin to road tar.
Manufacturer Directives and Chimney Safety
Meticulously review the stove manufacturer’s manual or usage guidelines. While manufacturers might indicate that operating a stove at very low temperatures overnight is feasible, they often overlook the detrimental impact on the chimney or flue, which could escalate the risk of a chimney fire.
Mitigating the Risk of a Chimney Fire
To mitigate the risk of a chimney fire:
- Regular Sweeping: Ensure your chimney is swept regularly:
- Smokeless fuel: At least once annually.
- Seasoned wood: Quarterly when in use.
- Bituminous coal: Quarterly when in use.
- Oil: Once annually.
- Gas: Once annually.
- Qualified Sweep: Engage a qualified chimney sweep. Contact the National Association of Chimney Sweeps (NACS) for details of proficient sweeps in your vicinity.
- Appropriate Appliance Size: Select a stove or appliance of suitable size for your room. An oversized stove may fail to combust all the fuel in the wood, resulting in unburnt material entering your chimney or flue, which could ignite.
- Proper Wood: Only burn well-seasoned wood with a moisture content below 20%. Utilise moisture meters to verify this.
Consequences of Chimney Fires
Chimney fires can result in catastrophic outcomes. Should the fire breach the flue, it can swiftly spread throughout the property. Even if confined within the flue, temperatures can surpass 1000°C, causing structural damage to the flue or liner. Chimney fires can fissure chimney walls and damage chimney pots and cowls.
Manufacturers recommend replacing a stainless steel flue post-chimney fire due to the thermal shock potentially fracturing the flue and liner, rendering them unsafe. Smoke detection within the property during a chimney fire signifies a breached flue, deeming it unsafe for further use.
Recommended Actions
If you suspect a chimney fire, immediately contact the Fire Brigade. Even if the fire appears extinguished, it could reignite. The flue should be inspected for any hot spots.
If you suspect a chimney fire has occurred in your property, have the chimney or flue assessed by an experienced professional before reusing it.
Always enlist experienced professionals for the installation of your appliance and flue liner. Adhere to the recommended usage guidelines post-installation to ensure safety.
By comprehending the causes and indications of chimney fires and implementing preventive measures, you can safeguard your home against the perils associated with these potentially devastating events.
