It is a fact that using your wood burning fireplaces, stoves, and inserts causes them to get dirty. Very dirty. It is necessary to get the chimney swept and dispose of the debris, as you know from what to expect when getting your chimney swept. But this is the perfect time to discuss another inescapable factor of a wood burning appliances: creosote.

So what is creosote?

Creosote Buildup

Creosote is a chemical mass of carbon formed when wood, fossil fuels, or tar is burned. Creosote distills and lingers commonly in a fireplace or a masonry chimney. When it is not removed, it can build a thick, hard coating of debris up the flue and chimney, posing a threat to your fireplace.

Creosote comes from unburned fuel that can eventually cause a chimney fire if not periodically removed. Creosote restricts the airflow of your chimney, preventing proper circulation and lowering efficiency. It is a combustible material that is also toxic. You don’t want to be breathing this in, or letting it catch fire.

There are three main types of creosote.

  1. First Degree Creosote is soft and sooty, not really all that different than wood ash.
  2. Second Degree Creosote is kind of like honeycomb toffee only not tasty. It is soft and crumbly, and indicates that you may have had a chimney fire.

Third Degree Creosote is a black, glassy, tar like substance, also called glaze creosote. It requires a special piece of equipment with rotating chains to remove.

Why is it bad?

Man cleaning chimney

It is important to have your chimney cleaned of creosote with an annual inspection. Creosote buildup also insulates the chimney from the heat of the exhaust gases, which impacts chimney performance. You want your chimney to warm up to aid in the rising of exhaust products. A cold chimney, caused by creosote buildup, will cause even more creosote to form. Inspection of the chimney lining is important to ensure the integrity of the chimney. Keep in mind that this is more a concern for wood burning fireplaces, stoves, and inserts, but you should still have a technician check your gas fireplace during your annual inspection as well.

Knowing the dangers of allowing creosote to build up in your chimney, whether you have a wood burning fireplace, stove, or insert, will help you keep your family and home safe. Remember to have your chimney swept at least once per year by a professional, or if you are using gas appliances, don’t forget the annual inspection.

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