Chimney Fires are caused by build up of cresote in the chimney. Wood does not burn completely and the natural chemicals in wood will vaporize, drift up the chimney, then condense along with the water vapor from the burnt wood. This mixture adheres to the chimney wall and will burn causing the chimney fire. The more creosote that builds up in the chimney, the greater the chance of a chimney fire. Chimney fires cause $200 million in property damage annually and result in 150 deaths per year. Bird nests and other chimney obstructions can also cause chimney fires and carbon monoxide poisioning.
An annual chimney clean-up can reverse chimney obstructions and creosote build-up. Creosote may look like glazed molasses or crusty burned marshmallows.
Creosote will build up fast when burning green or wet wood. The more water that's in the wood, the more water vapor that can condense in the chimney, and water vapor forms creosote. So keep your woodpile dry and use only seasoned wood. Don't run your fireplace or soodstove with the damper way down. This smoldering fire burns very inefficently; it leaves a lot of combustible vapors to rise up the chimney, and condense into creosote. The smoke is also cooler and doesn't rise as fast. The almost closed damper slows down the draft and the smoke-flow. Rather than closing the damper way down, you can reduce the heat by putting less fuel or use smaller pieces of wood.
Open fireplaces burn cleaner than airtight wood stoves because fireplaces can draw large volumes of air into the fireplace for efficient combustion. This large volume of air means smoke moves rapidly up the chimney with little chance to condense. This means less creosote, but also less heat. When using a wood stove or fireplace insert we get more efficient heating, but we have to check more frequently for creosote build-up.
A chimney rising through the center of a house will not build up creosote as fast as a chimney on the outside wall of a house, due to the cold air on the chimney's outside wall which will cause more condensation of the chimney's gases.
A chimney sweep will probably clean your chimney for less than $100 and some sweeps will make an inspection for no charge. It's a good investment in your family's safety..