Enlist these techniques to reduce the likelihood of a chimney fire starting on your watch.
There are more than 25,000 chimney fires incurring $125 million-plus in property damage every year in the United States. That damage is largely due to flames in the lower chimney migrating upward to crack, warp, melt, or otherwise negatively affect the masonry or metal chimney walls. In the most severe cases, chimney fires can destroy houses and put lives at risk. These tragedies are often preventable: Failure to regularly inspect, repair, and clean a chimney can cause it to malfunction or collect dangerous build-up that puts your family at risk.
Fortunately, if you practice the prevention tips here, that hard-working column above your fireplace or wood stove should continue to do its job of ushering smoke and other by-products out of your home, so you and yours can safely enjoy cozying up in front of the flames. Keep reading to understand what causes chimney fires and the six best steps you can take for preventing them.
1. Minimize creosote build-up.
The main culprit of chimney fires is creosote. This highly flammable, dark brown substance coats chimney walls when by-products of a fire (smoke, vapor, and unburned wood) condense as they move from the hot fireplace or wood stove into the cooler chimney. If the temperature in the chimney flue (the space inside the chimney) is high enough, and the creosote build-up thick enough, creosote can catch fire—and that fire can spread and move up the flue.
To minimize creosote build-up, only burn seasoned hardwood that has dried for at least six months and contains a moisture content of no more than 20 percent, which you can easily test with a wood moisture meter (available at hardware stores for $40 and up). And remember to always keep the damper (a metal plate in the flue that regulates the draft) open during a fire to maintain adequate airflow.
And if your chimney’s flue liner (the layer between the flue and chimney walls) is uninsulated, it’s recommended to insulate it by either wrapping a heat-resistant insulation blanket around the liner or pouring an insulation mix like vermiculite (available at hardware stores for $10 at up) into the space between the flue liner and flue. An insulated flue liner will prevent flue temperatures from getting too cool—a condition that could encourage fire by-products to condense and form creosote.
2. Schedule an annual chimney inspection.
Because many defects that lead to chimney fires, such as a cracked flue liner, aren’t visible to the naked eye, it’s crucial have a Chimney Safety Institute of America-certified chimney sweep inspect your fireplace or woodstove, chimney, and venting system once a year. This pro will inform you of any damage and, if desired, repair it as well as remove soot, creosote, or obstructions such as bird nests.
Consult your chimney sweep company about which inspection level is recommended for your chimney and venting system.
3. Clean your chimney when walls have 1/8 of build-up.
If when you scratch a finger against a chimney wall and uncover one-eighth of an inch of build-up, it’s time for a cleaning. A professional chimney cleaning costs between $100 and $350 and usually includes a sweep of the outside of the chimney along with the firebox, the smoke shelf, the smoke chamber above the firebox, the flue, and the flue liner.
4. Install a chimney cap.
Leaves and animal nests inside a flue can quickly fuel a chimney fire when touched by loose embers from a fire. A chimney cap on the crown around the outside opening of the flue will keep debris and critters out. The cap will also prevent “back puffing,” whereby escaped smoke from a fire re-enters the chimney and then the home. Caps also prevent acidic rainwater from entering and corroding the chimney. Expect to spend anywhere from $50 for galvanized metal caps to $500 or more for decorative models. While some homeowners opt to put in a chimney cap themselves, self-installation may void the warranty—it may be worth it to call a pro.
5. Use safe fire starters.
Always stick to the best fire starters when selecting fuel, kindling, and tinder. Well-seasoned hardwood or CSIA-approved logs are the only fuels you should use in your fireplace or wood stove. Never use gasoline and kerosene to start a fire—these liquids are highly flammable and combustible and can quickly create a conflagration. Likewise, don’t burn coal unless you’ve got a coal-burning wood stove because it can significantly raise the temperature of the flue, increasing the risk of a chimney fire. For kindling, stick to dried twigs or branches. Cloth is a poor choice—it gives off large amounts of smoke when it burns. Use torn or crumpled old newspaper or pine cones for tinder. Never use cardboard or glossy paper (like magazine pages) as tinder because both contain chemicals that can emit toxins into the chimney and the home when burned.
6. Employ clean burning techniques.
Low-temperature, slow-burning fires, particularly those left to smolder overnight, produce more smoke and leave behind more unburned combustible material. When that hardens into creosote on the chimney walls, there’s an increased risk of chimney fires. Hot, fast-burning fires, on the other hand, leave far less smoke, vapor, and unburned wood behind, so little to no creosote forms. The best way to burn a clean fire is to use the top-down burn method: Place the large logs vertically at the bottom of the fireplace or wood stove (with the bottoms of the logs facing you), add four to five horizontal layers of kindling, then top with tinder and light.
And, before retiring for the night, always extinguish the fire: Spread out the wood and embers with a fireplace poker, then cover them with the ash lying at the bottom of the fireplace using a fireplace shovel. Then douse the cooled wood and embers with enough baking soda to cover them completely—the sodium bicarbonate will extinguish any remaining embers. After the firebox cools (for a minimum of three hours, but preferably eight), shovel the ashes into a metal container. Fill the metal container with water and store it outside the home away from other flammable materials until you’re ready to discard them.