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Maintain Your Chimney and We Might Not Have to Visit Your House

November 2, 2012

It’s fall and heading toward winter.  With temperatures dropping, I’ve started using my woodstove again and I’m betting many others have too.  The question is how many chimneys have been cleaned this heating season?

A chimney’s job is to move smoke and products of combustion out of the home safely.  One product of combustion is water vapor (believe it or not).  Of course smoke and all products of combustion are hot when they’re produced.  As these products of combustion move up your chimney, they cool down, and eventually water vapor begins to condense on the inside of the chimney.  That condensation traps other products of combustion.  The water then evaporates leaving behind a built up layer of ‘creosote’.  At the point where the chimney penetrates the attic insulation level there is usually a big temperature change and much creosote is deposited at that level.  The term creosote is a bit of a misnomer.  Real creosote is a type of tar used to preserve wood.  It’s the black stuff on railroad ties.  Chimney creosote is not quite the same thing but it looks and burns the same, so the name has stuck.

Woodstoves and fire places are designed for high temperatures but chimneys are not.  Burning creosote in the chimney puts high heat where it’s not supposed to be and bad things begin to happen for the homeowner.  Elevated temperatures from a chimney fire cause both brick chimneys and metal stove pipes to expand or crack from the heat, leaving gaps in a once contiguous chimney.  Now products of combustion are no longer contained to the chimney and the home may be exposed to fireplace heat and smoke.  As the Chimney Safety Institute of America says, “One chimney fire may not harm a home.  A second can burn it down.”

Avoiding chimney fires requires two preventative measures:  technique and cleaning.  Using dry, seasoned wood will produce much less water vapor inside your chimney.  Also burning so that smoke gets up and out of the chimney quickly will help.  The more time smoke spends in your chimney, the more creosote is being deposited.  Fires that burn for a long time with a low damper setting are depositing more creosote than hotter, shorter-duration fires.

All fires will produce some creosote build-up.  So the second preventative measure is annual cleaning and inspection.  Cleaning removes creosote so there is no fuel for a chimney fire.  Inspection finds any damage to your chimney so you can repair it.

People who practice good woodstove and fireplace technique and have their chimneys cleaned and inspected annually don’t have chimney fires.  People who don’t follow these rules wind up meeting us face-to-face with axes and hoses in their living room.

If you have any questions on chimney fires, you can call us at 466-4602, e-mail me at dbleeker@scfd9.org, or post your question on this blog.  You can also check out the Chimney Safety Institute of America at www.csia.org.

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From → Fire Prevention

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