As the heating season winds down, it’s a perfect time to have your annual HVAC inspection and maintenance, including an annual chimney inspection. Chimney inspection? You may ask. Yes. It’s a good idea to have your chimney inspected annually and almost essential if you have a wood-burning fireplace. Here’s why:
Soot and Creosote Build Up
Over time, and depending on how often and how long you use your fireplace, there will be a buildup of soot and creosote in your chimney. Creosote forms when the chimney is cool and flue gases condense, becoming a combination of water, wood alcohol, and unburned fuel carbon particles. The resulting tar-like substance is highly flammable, and a risk for a chimney fire—definitely something you want to avoid.
What Happens in a Chimney Fire
A chimney fire occurs when the accumulation of unburned soot and other flammable residues (creosote) ignites. These compounds burn very hot and have a lot of energy. It’s not unusual to incur damage to the chimney from the intense heat and to have the exhausting flames and embers ignite the roof or other flammables nearby. Often the fire can only be controlled by the fire department. (In a worse-case scenario you could have flames shooting out of the top of your chimney with an accompanying freight train-like roar inside your home.)
Safety Measures and Best Practices
There are things you can do to minimize creosote build-up. Experienced wood-burning aficionados recommend burning only well-seasoned (properly dried) hardwoods. Burning fires large enough and long enough to keep adequate heat up the chimney is essential. Keep in mind that it’s when the chimney is too cool that creosote forms. Chimney temperatures need to be maintained at 300° F or higher to avoid creosote formation. As a result, most experienced wood-burners avoid burning in the spring and fall when it’s less desirable to have a long, hot fire.
What About Gas and Oil Furnaces?
Even with gas-fired furnaces and water heaters, your chimney should be part of your annual inspection and maintenance routine. Although gas fires can accumulate soot, it’s very rare. But chimneys can get birds and squirrels in them, even raccoons and other larger critters. An annual inspection is always a good idea to keep your system running efficiently and safely.
Chimneys for oil furnaces can also get clogged with oil soot, which is also flammable, although less so than wood creosote. Oil furnaces should be tuned up every other year, oil boilers every year, and the chimney should be checked at the same time.
When Should I Have My Chimney Cleaned?
If your chimney is attached to wood-burning equipment, you should have it inspected annually. Your inspector can advise you on when to have it cleaned, but typically every three or four years should be sufficient. Again, your usage can change that estimate significantly.
Be sure you have a qualified, experienced professional do your cleaning. Chimney sweeps are best prepared to work with creosote and extremes of solid or oil soot. Gas chimney inspection and cleaning can usually be handled by your HVAC pro.