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Why Is Creosote So Dangerous?

Wood smoke contains a famously hazardous substance called creosote, which is deposited inside chimney flues. You may wonder, ‘Why is creosote so dangerous?’ That’s a great question, and, fortunately, we have the real down-low on creosote. You see, creosote shows up in four different forms in chimneys (not just 3, as most sources say). Each has a distinct threat level, partly due to the difficulty of its removal. Below, we give you some hard-to-find facts about creosote, hints on what you can do to minimize it, and more.

Chimney Sweeping in Mechanicsville VAWhat Exactly is Creosote?

Creosote is a natural bituminous oil that is created when wood is burned. It results from the incomplete process of combustion. Cooler fires produce more of the sticky substance. Creosote consists primarily of two components (which also helps to answer the question, why is creosote so dangerous?): 

  • Methanol (wood alcohol), a toxic chemical, and 
  • Acetic acid. 

Acetic acid tends to trap carbon from the wood smoke. This flaky substance, creosote, dries, and bakes inside flue pipes. It is highly flammable, and a floating ember can easily ignite a chimney fire. Any creosote in a chimney could become the fuel that feeds a chimney fire, which often has devastating consequences. 

Creosote and the Temperature of Fires

Creosote will condense on the surfaces of chimney flues at temperatures below 250ºF. Creosote deposits are thicker and stickier, more like tar, if the temperature is below 150ºF. Because the exhaust gases from wood stoves get cooler than those produced in fireplaces, creosote is more of a problem with wood stoves than fireplaces. Well-insulated chimney flues tend to have fewer creosote deposits. 

What Type of Firewood Produces the Most Creosote?

There are two basic types of firewood, those being softwoods and hardwoods. Softwoods include pine, spruce, cedar, and Douglas fir. Examples of hardwoods are walnut, birch oak, hickory, and maple. 

All firewood should be seasoned, which means that the moisture level in the wood is below 20%. When green or moisture-rich wood is burned, the fire’s heat goes toward eliminating the moisture. That’s why such fires produce so much smoke. The type of wood fires that form the most creosote are those which use unseasoned softwoods. 

The Four Types of Creosote

Most sources will tell you there are three stages of creosote. Here is the real answer:

  • Stage 1 Creosote is: Condensation
  • Stage 2 Creosote is: Liquidation
  • Stage 3 Creosote is: Solidification
  • Stage 4 Creosote is: Friable-State (Easily Crumbled) Creosote

Details of each are lengthy and complex. The bottom line is that one is sooty and easy to remove; one is flaky and more difficult to remove; and one is like tar poured down a chimney, sometimes impossible to remove. Friable-state creosote is what you get when solid-state creosote burns. It is as easy to remove as sooty creosote but setting fire to a chimney to clean out the creosote is an almost certain path toward homelessness.

creosote and soot build up in Mechanicsville VAContact the Chimney Experts for Creosote Removal

Due to the risks associated with solid fuel heating appliances, it is best to trust truly qualified chimney sweeps for chimney maintenance. The chimney technicians at Chimney Saver Solutions are CSIA-certified and, among many other things, understand why creosote is so dangerous. They also have the right tools for creosote removal, no matter which stage it is in inside your chimney flue. 

Contact us for chimney inspections, creosote removal aka chimney cleaning, masonry repair, fireplace installation, chimney cap installation, chimney crown repair, and all of your needs related to fireplace and chimney maintenance. Call 804-440-5000 or fill out our online form

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