Chimney Fires


People in the town where I live burn a fair amount of wood. Each year we fight fires caused by what's said in the above link. We have been lucky, only ever lost one complete structure because no people were home and the house was fully involved when we were paged out. That said, there is an excellent piece of an article from Wiki which I will post in its entirety (because this is an important thread):

"Creosote in Chimney Flues

Burning wood and fossil fuels at low temperature causes incomplete combustion of the oils in the wood, which are off-gassed as volatiles in the smoke. As the smoke rises through the chimney it cools, causing water, carbon and volatiles to condense on the interior surfaces of the chimney flue. This leaves a black oily residue referred to as "creosote", which is similar in composition to the commercial products by the same name, but with a higher content of carbon black.

Over the course of a season creosote deposits can become several inches thick. This creates a compounding problem, because the creosote deposits reduce the draft (airflow through the chimney) which increases the probability that the wood fire is not getting enough air to burn at high temperature.

Since creosote is highly combustible, a thick accumulation creates a fire hazard. If a hot fire is built in the stove or fireplace, and the air control left wide open, this may allow hot oxygen into the chimney where it comes in contact with the creosote which then ignites - causing a chimney fire.

Chimney fires often spread to the main building because the chimney gets so hot that it ignites any combustible material in direct contact with it, such as wood. The fire can also spread to the main building from sparks emitting from the chimney and landing on combustible roof surfaces.

In order to properly maintain chimneys and heaters that burn wood or fossil fuel, the creosote buildup must be removed. Chimney sweeps perform this service professionally.

73% of heating fires and 25% of all residential fires are caused by failure to clean out creosote buildup.[4]

Since 1990 the number of creosote caused fires has decreased in the United States by 75%. [5] This is partly due to the use of efficient wood stoves that fully burn the volatiles in the smoke, and partly due to the decrease in the use of wood heating during two decades of milder Winter weather, and low fuel prices.

Two types of fuel are more likely to produce creosote buildup in the chimneys: wet wood and wood from trees with high oil content. Resinous softwoods such as pine and cedar are known to produce higher levels of creosote as well as particularly oily hardwoods such as Osage Orange.

The best practices to avoid chimney fires are:

Use a high efficiency stove or heater that fully burns the volatiles in the smoke.
Make sure the wood is dry before burning.
Avoid burning wood from trees with high oil content.
Clean the chimney annually. "