Why Does Creosote Build Up? - Sacramento CA - A to Z Chimney
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It’s a known fact that burning wood in the fireplace results in a buildup of creosote in the chimney. But why is that? Do some chimneys accumulate creosote faster than others? And is there anything that can be done to reduce the buildup of dangerous creosote in your chimney?

Why does creosote build up in chimneys?

Creosote is a byproduct of incomplete wood combustion. When wood burns, creosote forms and is carried upward by smoke. As the smoke cools within the chimney, creosote-laden condensation forms on the walls of the chimney, where it hardens and can pose a fire hazard. Note, however, that creosote is a result of INCOMPLETE wood combustion. Creosote itself will actually burn up if the fire is burning hotly and efficiently.

Why do some chimneys accumulate creosote faster?

Because creosote does burn up in a hot, efficient fireplace, some chimneys do, in fact, accumulate creosote faster than others. Wood begins to break down chemically at 500 degrees Fahrenheit. Once the temperature of the fire reaches 1,100 degrees, the gases and creosote the result from wood combustion also burst into flame. EPA-rated fireplace inserts, air-tight fireplaces, and woodstoves often generate temperatures in excess of the 1,100 degrees Fahrenheit, meaning those types of appliances will send much less creosote up the chimney than open-hearth fireplaces or older, less efficient fireplace inserts or wood-burning stoves.

In any fireplace, however, the smoke cools as it travels up the chimney. Any smoke that cools below that 1,100 degrees before the creosote burns will leave condensation on the chimney walls. Because the smoke reaches those cooler temperatures before exiting the chimney, some chimney types will accumulate more creosote because of their bends and crooks. Those types include:

  • metal chimneys,
  • chimneys that are located on exterior walls,
  • chimneys that don’t draft efficiently,
  • chimneys that are too large for the fireplace and chimney

What you can do to lessen creosote buildup in your chimney:

Once you know the science behind creosote formation, and that cooler fire temperatures lead to more rapid creosote formation, there are steps you can take to slow the buildup of creosote in your chimney. There are two factors to take into consideration when aiming to reduce creosote formation: You need to make sure that your fires are burning hot and that smoke is exiting your chimney quickly and efficiently. Some things you can do to slow creosote buildup include:

  • Burning dry firewood that has been properly seasoned,
  • Keeping the damper fully opened every time you burn a fire,
  • Maintaining a hot, vigorously burning fire,
  • Monitoring the temperature of your fireplace or chimney to ensure its burning hot enough to ensure creosote combustion,
  • Making sure your chimney flue is properly sized for your fireplace, and
  • Replacing inefficient open-hearth or outdated fireplace inserts with newer efficient EPA-certified models.

Of course, stemming the dangers of creosote buildup in your chimney begins with annual chimney sweepings and inspections. If you’re due to have your chimney swept and inspected, call A to Z Chimney Services to schedule your appointment today!