Creosote Buildup

What is so Risky About Creosote Build Up?

Creosote can buildup in your chimneyWith the Fall and Winter chill in the air, you’re probably getting ready to light up that fireplace (or maybe you already have)…sounds good right?

But wait, when was the last time you had your fireplace and chimney inspected for creosote buildup? So, if it’s been awhile, you should ask yourself this question…”Is my fireplace and chimney safe to use?”

One of the most common fire hazards from your fireplace is the natural build up of creosote. This hazard is especially common in wood burning fireplaces and wood stoves.

What is Creosote?

Soot and creosote are by-products of burning wood and are formed out of the smoke going up the chimney. Although we call it smoke, and it looks like smoke, what it actually is, is flue gases that are released as the fire is burning. As the gases travel upward,  they are passing over the cool walls of the chimney. We all know what happens when warmth passes over a cooler surface, condensation occurs. This condensation is carbon based, which results in creosote being deposited on your chimney walls.

These deposits accumulate on the inside of the venting system; i.e. stovepipes and chimney flues, are are flammable and, if the build up is left to continue to build, it could get to the point that it will restrict the flow of flue gases. Not only is this a fire hazard, but obstructed flues can send toxic gases (smoke) back into the home, putting you and your family at risk.

Creosote tends to be deposited more heavily where the chimney is the coolest. Therefore, the area  just above the opening of the fireplace or wood burning stove may look clean and safe, but that can be deceiving, because the heavy buildup will be found higher in the flue.

3 Degrees of Creosote Buildup:

  1. The first degree creosote is basically soot and relatively easy to clean off with a chimney brush. This type of creosote occurs when the wood is very combustible and there is good air flow up the chimney, allowing the gases to move upward and escape quickly.
  2. The second degree creosote develops when incoming air is restricted (usually caused by glass fireplace doors or wood stoves.) This type of creosote resembles shiny black flakes, is heavier that first degree creosote, and more difficult to clean off.
  3. Creosote buildup in the third degree is the most dangerous and hardest to remove of all. Rather than black shiny flakes, it appears as tar, either coating or running down your chimney. This condition can often be seen by either looking up the flue or at the top of the chimney.

What should you do?

Burning Wood in your fireplace creates creosoteIf you burn wood, your chimney should be inspected and cleaned frequently.

  • Burning green wood can make a heavy creosote deposit quickly.
  • Burning dry wood, and periodically burning a hot fire can help reduce the buildup.
  • There is no substitute for a careful and competent chimney inspection and cleaning.

So before you get too cozy in front of that fireplace this winter – be sure it’s been checked out and it’s safe.

In my next couple of articles, I’ll share some ideas that will help reduce creosote buildup and how to tell if your chimney is on fire.

**originally published 08/11/11

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