Preventing Chimney Fires

As fires burn, smoke goes up the chimney. Some of that smoke condenses in creosote on the flue -- the inner surface of the chimney. Creosote, a hard tar-like substance, builds up over time. When a thick coat of creosote catches fire, you get a chimney fire -- a powerful and frightening inferno that can be as loud as a low flying jet.

Chimney fires are often so hot that nearby walls and rafters burst into flame. The fire spreads so fast that firefighters often arrive too late to save any of the home.

Not all chimney fires are loud roaring events, but quiet ones can be just as dangerous. The extremely high temperatures associated with chimney fires cause cracks to form in the flue and chimney. Carbon monoxide is generated anywhere fuel is burned, including your fireplace, woodstove or furnace. Normally, these deadly fumes vent safely up the chimney. But if the chimney starts to leak, the fumes may be drawn back into the home.

Carbon Monoxide

Carbon monoxide is a sneaky poison. The odorless colorless gas can be lethal. The human body treats it as if it were oxygen. Quickly distributed throughout the body, the poison has the biggest effect on the brain. Children can sustain brain damage with low levels of exposure. Symptoms mimic the common cold, so most people are unaware they are being poisoned. More extensive exposure leads to vomiting, nausea and, eventually, death.

The good news is that your fireplace can continue to be a source of safe pleasure if you stick to a simple maintenance schedule. Have your chimney cleaned regularly and inspected by a chimney sweep trained in chimney inspection.

Here are answers to some of the most common questions:

Q: How often should I have my chimney cleaned?

A: The Chimney Safety Institute recommends that if you light fires in your fireplace or woodstove three or more times a week during the heating season, you should have your chimney cleaned and inspected once a year. If you burn unseasoned wood (wood that is still a bit wet or green), twice-a-year cleaning and inspection may be necessary.

Q: If I keep a small fire going most of the time, will I need to clean the chimney more often?

A: Most of the creosote build-up occurs when the fire is first lit. A cold chimney causes much more of the smoke to condense on the chimney flue. Therefore, a continuous fire will usually foul a chimney more slowly than many separate fires.

Q: How much does it cost to have my chimney cleaned?

A: Typically, an inspection will run about $30-$50. A cleaning goes for about $60 to $130, depending on the difficulty level. However, major chimney repairs can cost thousands of dollars. Most major chimney problems can be prevented with regular preventive care.

Q: What is a chimney liner?

A: Nearly all new chimneys have chimney liners. Chimney liners may be made of metal, tile or cement and create a smooth, airtight path up your chimney. By increasing the distance between heat and combustible surfaces like rafters, liners can provide an extra level of protection from chimney fires. They also help prevent water from getting into the masonry work, where it can freeze and cause permanent damage to your chimney. Many efficient furnaces require chimneys with precisely sized chimney liners.

Q: Do I need to have the flue from my furnace cleaned too?

A: Yes. Whenever you have your chimney cleaned, have the furnace flue cleaned at the same time. While furnace flues are typically less susceptible to creosote build-up, they do get fouled with sulfur and chlorine. Allowed to accumulate, these chemicals combine to form a powerful acid that eats away at the flue.

by David Hollies, reprinted courtesy of HomeAdvisor.com