Creosote is an unavoidable byproduct of burning wood. It can be thought of as wood smoke, condensed. If we use wood as a fuel source, then creosote happens.

Here’s an example: Think of how a gas engine with a choke left on gets smokey. Like that, creosote is wood which has been heated to the point of making smoke but has not engaged in the combustion process.

Tech holding creosote from a fireplace

Okay But… What Is Creosote, Exactly?

Creosote = Particles of charred wood + Vapors cooled to a liquid & dried to a semi-solid + other organic compounds.

As with our gas engine example, the smoke is unburned gasoline, so creosote is wood which could have burned in our fireplace but tried to leave (to escape through the chimney) without combustion. As a result, it gets stuck on the flue walls and builds up over time.

Is Creosote Dangerous?

The short answer, YES.

But as with most things life, it’s not that simple. 

Creosote build-up in a system is itself flammable. It is the fuel source to the dreaded chimney fires so often reported in the colder time of year. Since creosote cannot be entirely avoided, efforts should be made to minimize its buildup and to remove it before it becomes a fire hazard.

Flue After a Chimney Fire
Flue After a Chimney Fire

How Much Build-Up is Too Much?

Excessive creosote production is often the result of poor burning practices. Misuse of a wood-burning appliance includes large fuel loads in the firebox (adding too much wood), damp or green wood, and limiting the amount of combustion air allowed in the firebox.

By consciously operating our wood stoves and fireplaces with smaller fires using seasoned/dry wood and giving the firebox sufficient air, creosote build-up is minimized.

Puffed Creosote - Evidence of Flue Fire

Puffed Creosote – Evidence of Flue Fire

Learning to use our wood-burning appliances responsibly helps, but some creosote accumulation is unavoidable. That’s the whole reason why the sweeping of chimneys became an industry!


Burning Wood Makes Creosote 

Creosote Makes Chimney Sweeping Necessary. Many new (or sometimes misinformed) homeowners quickly learn that chimney fires ruin flues and chimney fires can easily spread to other parts of a home. Since a fire in our home is unthinkable, the proper course of maintenance is an annual sweeping of the chimney.

(Some of our customers even invite us out twice a year, due to heavy use of their fireplace or insert stove!)

Creosote from inside a chimney

Along with the fire danger associated with creosote, there are other reasons to keep up on our service requirements. Most homeowners also report that it is extremely smelly, and gives the chimney a foul odor, especially in the damp time of year.

Creosote is corrosive, damaging the flue and connector components if left in the system. There are few home maintenance chores as unglamorous as having us sweep your chimney, but none are more important.

Let’s Recap What We’ve Learned

5 Quick Facts

  • It is a combustible material that acts as a fuel waiting to ignite inside the chimney.
  • Creosote from burning wood is unavoidable, but it can be minimized.
  • It can only be removed when it is at a manageable amount, excessive build-up cannot be easily swept away.
  • Odors and corrosion are a result of creosote lingering in a chimney (and is one reason customers call us for a chimney sweeping).
  • Easy steps can be taken to minimize the accumulation of creosote in a chimney.
  • An annual inspection and chimney cleaning are necessary for optimal performance and home safety.
Watch this quick and simple video demonstrating how this messy substance is removed from a chimney. Note the steps taken by Full Service Chimney to ensure your living room stays as clean as when our chimney sweep arrives!

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