A Fire Safety Concern – Effects of Winter On Your Chimney

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Winter weather, especially a wet winter with ice, rain and snow, can take its toll on your chimney.

Under mild, damp weather conditions, fireplaces do not burn not as hot and clean as they do in cold dry weather, resulting in faster creosote build-up inside a chimney which creates a fire hazard. This highly flammable substance is contained in only a quarter inch of soot and develops in several stages.  Initially it forms flaky soot which is easily brushed away, leaving safe and clean flue walls. Left alone, creosote hardens into a brittle deposit which is more difficult to remove.  In the final most dangerous stage, creosote buildup acquires a dense, shiny tar-like in appearance. At this point the residue has basically wood tar which has baked onto the walls of the chimney or flue lining.  A fire fed by this substance is extremely difficult to extinguish.

The amount of smoke, the temperature of the fire and the regulation of air are the major variables which determine the amount of creosote build-up. When fires burn at low, smouldering temperatures which typically happens in wet mild weather, the combustion process is incomplete, so instead of burning off, by-products can contribute to the accumulation of creosote deposits in the chimney liner.  This is a highly concentrated fuel that resembles a coating of tar dripping down inside of your chimney liner, which can easily ignite in a hot fire, potentially starting a house fire. The key is to preventing this is to remove creosote during its first stage of build-up when it is flaky and easy to remove before it reaches the glazed stage.

To minimize creosote buildup, avoid burning fires that are slow and smoldering; keep fires hot and with plenty of air; avoid burning newly cut, unseasoned wood or artificial packaged logs and have your chimney swept often.

If your chimney is not properly capped, snow and ice can fall inside your chimney causing moisture damage. This not only affects the chimney’s masonry but can also make lighting fires much more difficult.  Water doesn’t have to fall into your chimney to cause water damage. The mortar, or cement mixture between each brick is often more porous than the bricks themselves, so when winter brings wet weather, all of that moisture can seep into the mortar.  This can cause a lot of damage, including cracking and crumbling mortar, cracked bricks, crumbling masonry work, and the shifting of the entire chimney.

During the winter, an improperly capped chimney is also susceptible to falling debris such as leaves and sticks which can find their way into your chimney through even the smallest opening.  Critters including mice, rats and birds love to find warm and dry places to call home during the unforgiving winter months and can create nests which can block a chimney creating a potential carbon monoxide and fire hazard.

Make regular chimney cleaning part of your home safety maintenance plan.  An annual chimney inspection and sweep by a qualified service technician will ensure it is in safe operating condition.  During a mild wet winter like this year, give your chimney an extra sweep mid-winter. Like having working Smoke and carbon monoxide alarms and a Home fire escape plans, chimney cleaning should be a regular part of your home safety maintenance plan.

Courtesy of the Cavan Monaghan Fire Department

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