Chimney Fire Prevention

A chimney fire may not sound like much of a risk or much of a problem. After all, the chimney is well insulated. It may seem unlikely that the fire will get to the rest of the house if it even gets started in the first place. But dirty chimneys are susceptible to fires that, at their worst, can destroy homes and kill the inhabitants.

Chimney fires can catch on explosively, shooting flames and dense smoke out the top. Or they can be slow-burning and barely noticeable until they've gotten hot enough to damage the chimney irreparably and even catch your house on fire.

With a little care, chimney fires are easily preventable.

First, let's understand how chimney fires happen. The wood you burn sends smoke up your chimney. That much is obvious. But it may not be obvious that the smoke doesn't have to remain in a gaseous form. Wood smoke contains significant amounts of material that can condense on the sides of the chimney's interior. The result is a tar-like or flaky substance called creosote. Once it's formed, the creosote remains stuck to the inside of the chimney, just waiting for a flame or spark to reach up and set it off.

Any wood can create creosote, but unseasoned wood is the worst culprit. Colder than normal temperatures can encourage higher than normal condensation of creosote. And restricted air supply can add to the problem.

Unseasoned Firewood

Burning green wood isn't an easy task. Green wood contains a lot more moisture than seasoned wood, and that moisture has to be removed somehow in order for the wood to burn. The resulting smoke is cooler than if seasoned wood had been used. Cooler smoke is more likely to come out of its gaseous state, condensing on the inside of the chimney.

Cold Temperatures

Cold on the outside of the chimney can also help cool the smoke down to the point where it condenses and forms creosote. If it's an exterior chimney, running up the side rather than through the center of the house, this adds to the possibility.

Air Supply

It helps to have good currents of air to lift the smoke out of the chimney before it condenses. If the fireplace can't draw air in freely, this interrupts the flow and, again, creosote forms. Closing the fireplace's glass doors or not opening the damper all the way are the main ways in which air supply gets restricted.

In addition to all this, remember that large, compact bundles of wood tend to produce cooler fires. Build smaller, hotter fires instead. And don't burn cardboard boxes or wrapping paper in your fireplace. It's too easy for a flaming piece of paper to waft up the chimney and catch things on fire.

But most importantly, have your chimney inspected and cleaned regularly. Nothing can completely prevent the creation of creosote. But a certified chimney sweep can keep the problem from getting out of hand.

Here are some additional links that you might find helpful:

The Facts about Chimney Fires

Greenland N.H. Volunteer Fire Department article