Chimney fires occur when deposits of carbon and dust accumulate in a chimney and are set alight by sparks or flames from an open fire. The deposits result when wood burns slowly and produces smoke, the smoke condenses on the cool inner surface of the chimney and a layer of creosote forms. Creosote is a highly flammable material. If it ignites at the base of the chimney, it can produce a raging fire that travels up the chimney at extremely high temperatures. Most solid fuels create some kind of soot which without regular cleaning of chimneys builds up in the flue and eventually catches fire.

How Are Chimney Fires Avoided?

Regular cleaning is the only way chimney fires can by avoided. The National Safety Council recommends that chimneys be swept thoroughly at least twice a year, once perhaps at the beginning of the cold weather period, i.e. after the summer/autumn, to clear the chimney of debris (birds’ nests, etc.) which may have accumulated and also to remove soot. They should also be swept mid-way through the winter to ensure a fire does not occur. Obviously the more often a fire is lighted and the more varied the fuels used, the more frequently it should be cleaned. Do not rely on chemical blocks, etc., to clean a chimney. There is no better method than a sweep’s brush!

Are They Dangerous?

Yes, chimney fires are particularly dangerous in that they can structurally weaken the flue liner and chimney block causing cracks to form into which sparks may enter and so breed fires elsewhere in the house. Burning soot may also fall on carpets etc. and set them alight.

What To Do If a Fire Starts?

• Close the glass doors and air inlets
• Get everyone out of the house, including yourself
• Call the fire department
• Use a garden hose to spray down the roof (not the chimney) so the fire won't spread

Why Do I Need a Chimney Inspection?

“A chimney inspection is like an annual dental check-up," states Ashley Eldridge, director of education at the Chimney Safety Institute of America (CSIA). "It's preventative maintenance that helps minimize potential hazards. Sometimes, maintenance requires extra diligence."

To reduce the risk of chimney fires, the CSIA cautions people that might be increasing their fireplace use in the fall and winter to put a chimney inspection at the top of their home improvement list. This caution is primarily directed at people who might increase their wood-burning fireplace usage from an occasional fire to a weekly activity. According to Eldridge, people who use fireplaces infrequently tend to be less informed about the important role that the chimney plays in exhausting the hot gases and smoke from a fire. When a chimney has creosote build-up, or is obstructed by a bird's nest or debris, it has the potential to catch fire and cause damage.

According to the U.S. Consumer Product Safety Commission there were 18,300 residential fires in the United States in 1998 originating in chimneys, fireplaces and solid fuel appliances. These fires resulted in 160 personal injuries, 40 deaths and $158.2 million in property damage.

Tips for Reducing the Threat of a Chimney Fire

• Add a chimney cap to the top of your chimney. A cap can keep out damaging moisture, which wears away masonry and other metal components within a chimney.
  
• Ensure that your chimney has an appropriate liner. Chimney liners are required in new construction to separate system emissions from the structure of your home.
  
• Have chimney flashing (the seal between the chimney and the roof) inspected and maintained. Flashing prevents rain water and snow melt from entering a house and causing costly damage to walls and ceilings.
  
• The National Fire Protection Association (NFPA) also recommends that all chimneys be inspected on an annual basis to prevent chimney fires.

Reprinted with permission from the Chimney Safety Institute of America, www.csia.org