An Unwanted Fire

If you enjoy your wood-burning fireplace or wood stove than you should be aware of the signs of a chimney fire.

Chimney fires are caused when the heat from a fire ignites creosote (that black, sooty, sometimes dry and flaky, tar-like and drippy, or shiny and hardened substance that clings to the sides of your chimney flue). Creosote is a natural by-product of wood burning. However, the type of wood you burn (hard, soft, wet, dry), how big a fire you make, how frequently you burn, the physical design of your fireplace, smoke chamber and flue, etc. will effect how much and which types of creosote is deposited on your flue. Often all 3 types of creosote will be present in any given flue.

Creosote build-up inside a flue

The National Fire Protection Association Standard 211 says, “Chimneys, fireplaces, and vents shall be inspected at least once a year for soundness, freedom from deposits, and correct clearances. Cleaning, maintenance, and repairs shall be done if necessary.”

The “at least” in that standard is meant to encourage users to have their flue inspected and swept more frequently than once per year when they are serious burners or when you know that you are burning unseasoned wood regularly.

There are generally 2 kinds of chimney fires – hard and fast or slow and low. The CSIA states that:

Chimney fires can burn explosively – noisy and dramatic enough to be detected by neighbors or people passing by. Flames or dense smoke may shoot from the top of the chimney. Homeowners report being startled by a low rumbling sound that reminds them of a freight train or a low flying airplane. However, those are only the chimney fires you know about.
Slow-burning chimney fires don’t get enough air or have fuel to be dramatic or visible. But, the temperatures they reach are very high and can cause as much damage to the chimney structure – and nearby combustible parts of the house – as their more spectacular cousins.

 

Three things to look for during a fire are:

  • a loud cracking and popping noise
  • a lot of dense smoke (coming from the firebox or the chimney outside), and
  • an intense, hot smell

 

What next? The damage from a chimney fire can be catastrophic.

When a chimney fires occur in masonry chimney – whether the flue is an older, unlined type or tile lined to meet current safety codes – the high temperatures at which they burn (around 2000°F) can “melt mortar, crack tiles, cause liners to collapse and damage the outer masonry material”.  Most often, thermal shock occurs and tiles crack and mortar is displaced, which provides a pathway for flames to reach the combustible wood frame of the house. This event is extremely dangerous, call 911 immediately. – (Source: CSIA)

 

Chimney fires can warp and twist pre-fab metal chimneys and wood stove connector pipes as well. If any damage is sustained to these parts they must be replaced before further use.

If you think you are having a fire, call 911 immediately. Firefighters will recommend that you have a CSIA certified sweep come and inspect the chimney afterwards to determine what steps need to be taken before you can burn again, if at all. Depending on the situation, you might need a few flue tiles replaced, a new liner system installed or an entire chimney rebuilt.

If you think that you’ve had a fire but aren’t sure, call today to schedule your annual inspection and sweep. If you hope to burn again this season it is better to be safe than sorry. Chimney fires destroy more than 25,000 homes per year (Source: CSIA).
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