Clonbinane Rural Fire Brigade - July 2017
Chimney Fires
Winter is here and this month’s fire safety snippet is on chimney fires. 
Chimney fires can occur when a hot fire in your wood heater, wood stove or fireplace ignites a build-up of creosote. Creosote deposits accumulate in all types of chimneys - masonry, or metal, where wood burning appliances are vented. Creosote is combustible and if it is set afire the resulting chimney fire is extremely hot. Roaring like a freight train, a chimney fire can melt through even a well-built "safe" chim-ney, setting the building on fire. Creosote is a black, oily wood-tar condensate that forms in chimneys over fireplaces or woodstoves is a black tarry condensate that forms inside of chimneys and flues when burning wood in fireplaces and woodstoves. Creosote tar, a natural by-product of burning wood is carried into the chimney as a vapour in the smoke. But this creosote tar vapour condenses as a liquid on to the cooler chimney sides as smoke passes up the chimney and flue. A long low-smouldering wood fire produces more creosote than a hotter faster-burning wood fire. That's because burning wood at a lower temperature results in more incomplete combustion of the wood itself. Incomplete combustion of a fuel results in a higher level of off-gassing of incompletely burned chemicals in gaseous form, including, in the case of wood fires, wood-tar .As the creosote deposits cool they harden to a shiny black coating that can be difficult to remove, especially if the creosote deposits are left over a period of time.
Creosote will continue to accumulate on chimney surfaces until it is removed. A chimney cap not only prevents rain from entering (and possibly damaging) the chimney, it improves draft and prevents downdrafts - conditions that can increase the rate of creosote formation. Creosote deposits may be removed by using a stiff chimney brush if the deposits are sooty in character. This is the easiest and best condition to handle. Creosote deposits that are glazed and hard on the chimney walls can be difficult to remove by may be removable using a powered mechanical brush.
Chimney fires can happen without you noticing it and can cause significant damage. Prevention and cleaning of the chimney is the answer.
Prevent the creosote building up by burning dry wood only. Ideally wood should be cut, split and dried a year before burning. Burn small hot fires as opposed to large smokey ones. This will help reduce creosote build up. A build up of creosote that is between 3mm to 6mm is considered a hazard and should be removed. Chimney sweeper brushes are available from your hardware store or wood heater specialist.
Should a fire occur in your chimney or flue pipe then remember a fire needs air to burn. Close all vents and doors. Use a dry chemical fire extinguisher and avoid the use of water. Extinguishing with water may burn you with steam, crack the glass in the firebox door or buckle metal work. If you think the fire is out then do not open the door for at least 30 minutes. Did you call the fire brigade? A good idea to do so as soon as you realise you have a problem. Some fires occur where the flue pipe goes through the ceiling. This can happen if the flue and heater aren’t installed by a qualified professional. A ceiling fire is extremely dangerous and requires immediate evacuation from the house and for someone to call 000 ASAP.
