Within the context of chimney fires, there exist a few basic types of fires.There are good fires and there are bad fires. Good fires help preserve the integrity of the flue and chimney system, while bad fires can destroy the system, and cause a chimney fire.

Good fires make the chimney feel warm and start slow with gentle warming until the inside of the chimney can adjust to the increase of heat. Warming the flue first with a rolled up piece of newspaper will help get the draft going quickly and will also insure the damper is open. It is too late when the fire is burning brightly and the home is filling with smoke to determine your damper was still closed.

To make a good fire, loosely stack a few medium logs over some kindling with a fire starter such as crumpled newspaper or commercial fireplace starters. Lighter fluid, gasoline, or charcoal fluids cause too much of an immediate heat rise and are not recommended. Remember the fireplace likes to gently warm.

Keep the fire burning well. Slow burning fires produce more creosote and allow it to collect on the chimney lining. If creosote has built up on the flue lining and a really hot fire is produced, you could start a chimney fire. This will clean the creosote from the lining but it will also cause damage to the lining.

Bad fires heat the flue lining too fast and do not allow for the lining material to gradually expand. Rapid expansion of the lining will cause cracks that will fill with creosote, heat at a different rate than the lining and cause larger cracks. The rapid heating of the lining will also cause the mortar to separate from the lining, causing more cracks. These cracks start slow and look thin. Over time with bad fires, the cracks get larger until the mortar is gone or the tiles break. These large openings allow heat, fire, or the products of combustion to escape to the surrounding areas of the flue and can possibly cause a house fire.

A bad fire can also cause a chimney fire. Chimney fires are the result of the excessive built up creosote being ignited from a really hot fire. "Hot" fires, are usually caused by extreme high temperatures or extremely high flames, like when excessive amounts of paper are burned, or flammable liquids are thrown into in the fireplace.
 
If a chimney fire does occur, DO NOT use water to extinguish the fire. Using water will produce a lot of smoke, soot, and steam. The smoke and soot will fill the house and cause damage. The steam in the flue will cool the tiles or pipe and cause extensive damage. Let the fire go out naturally or use a dry chemical fire extinguisher to slow the fire. Some of the extinguishing agent will go up the chimney to extinguish some of the fire and slowly cool the chimney. Always check outside the house to see if any of the burning embers have caused a fire. Watering down the surrounding area and the roof may be helpful. Do not spray water on the chimney to cool it. The water will cause damage.

Damaged linings may allow heat and fire to get out of the "sealed" flue system and contact surrounding combustibles adjacent to the flue, and may cause a fire which could burn down your house or at least damage it. Damaged linings may go undetected for years without proper cleaning or a big fire. Keep the flue system inspected and clean.

One way to inspect the chimney is with the use of the Chim-Scan®. The Chim-Scan® is a valuable tool for seeing where few people have seen before. A flashlight and even the most trained set of eyes can only see a fraction of what the Chim-Scan® sees. The Chim-Scan® is a video camera/still camera that can be fed into chimneys and ductwork to observe the interior surfaces. The camera is attached to rods and lowered into the chimney, where a video monitor attached to the camera allows the inspector to view the interior of the chimney. Once the inspector sees a crack in the lining, excessive creosote build-up, or any other type chimney anomaly, a photograph can be taken by the inspector. These photographs can either be printed on-site right away or stored to a disk to be printed and included in a full inspection report at a later time. The proper use of this tool can aid any certified chimney sweep or inspector in performing the recommended yearly inspections as set forth by the National Fire Protection Association. The Chim-Scan® can also aid a fire investigator in determining if the cause of a fire was an improperly functioning chimney.

So go ahead and build a fire in your fireplace and "Sleep well tonight."

Copyright 2003 Professional Investigative Engineers. All rights reserved.