Failing to maintain your woodstove or fireplace properly can lead to a chimney fire. Chimney fires occur when combustible deposits on the inner walls of the chimney ignite. These combustible deposits, called "creosote," are a natural byproduct of woodburning. A fire hazard exists if 1/4 inch of creosote (or more) coats the inner walls of the chimney.

Prevention. Chimney fires do not occur in clean, intact, properly installed chimneys. Have a professional chimney sweep clean and inspect your appliance at least once a year. More frequent cleanings may be required, based on the type of wood burned, the type of appliance, and the frequency of use. In general, an older, uncertified woodstove, or any appliance that is used frequently, will require more than one cleaning per year.

Detection. The first indication of a chimney fire is usually the noise—a roaring sound that grows louder as the fire’s intensity increases. Clouds of black smoke and sparks will be seen exiting the top of the chimney; in severe fires, flames can extend several fee about the chimney.

Action.
In case of a chimney fire, follow these steps:

1. Call the fire department immediately.
2. Alert others in the house to evacuate.
3. Close the appliance’s dampers and/or the primary air inlet controls, limiting the fire’s air supply and reducing its intensity. If there is a barometric damper in the chimney connector, plug or close the opening in the barometric damper.
4. Open the appliance door just enough to insert the nozzle of a 10 lb. dry chemical fire extinguisher rated for Class ABC fires. Discharge the entire content of the extinguisher into the appliance and shut the door.
5. If possible, wet down the roof and other outside combustibles to prevent fires ignited by shooting sparks and flames.
6. Closely monitor all combustible surfaces near the chimney. During severe chimney fires, these surfaces can become hot enough to ignite.

After a chimney fire, have the chimney inspected by a professional chimney sweep or woodstove/fireplace installer; choose a professional who has earned credentials from the National Chimney Sweep Guild, Chimney Safety Institute, or the HEARTH Education Foundation.

Contact your insurance carrier.

DO NOT USE THE CHIMNEY UNTIL IT HAS BEEN INSPECTED BY A PROFESSIONAL. The excessive heat produced by a chimney fire can crack chimney walls, damage chimney liners, and damage some types of factory-built chimneys. If not repaired, these damages create a greater possibility for any subsequent chimney fire to spread beyond the confines of the flue to the house

As firewood burns, it goes through three phases:

Water

Up to half the weight of freshly cut logs is water. After proper seasoning only about 20% of the weight is water. As the wood is heated in the firebox, this water boils off, consuming heat energy in the process. The wetter the wood, the more heat energy is consumed. That is why wet wood hisses and sizzles while dry wood ignites and burns easily.

Smoke (or flame)

As the wood heats up above the boiling point of water, it starts to smoke. The hydrocarbon gases and tars that make up the smoke are combustible if the temperature is high enough and oxygen is present. When the smoke burns, it makes the bright flames that are characteristic of wood combustion. If the smoke does not burn in the firebox, it may condense in the chimney, forming creosote.

Charcoal

As the fire progresses and most of the hydrocarbons have vaporized, charcoal remains. Charcoal is almost 100% carbon and burns with very little flame or smoke. Charcoal is a good fuel that burns easily and cleanly when enough oxygen is present. Of the total energy content of the wood you burn, about half is in the form of smoke, and half is charcoal.

The challenge in burning wood efficiently is to burn off the smoke before it leaves the firebox. The rest of the suggestions in this fact sheet will help you to get more heat from your wood, and reduce creosote deposits and air pollution.

2. Preparing Firewood

It takes 9 to 18 months for wood to properly season after it has been cut to length and split. Wood dries 10 times as fast through the end grain as it does through tangential sides. Splitting into smaller pieces will further speed drying. Dry, seasoned wood will ignite and burn much easier and cause fewer problems with condensation and creosote.

Green or improperly seasoned wood will be free of checking and cracks on the ends, will feel "heavier" and may even feel moist to the touch. Often it will give off more of an odor than dry wood. When it burns it will often sizzle and pop, and give off steam. It is not recommended for burning in a factory-built fireplace.

Firewood should be split and stacked under cover in the early spring to be ready for burning in the fall. After drying in the summer sun and warm winds, the wood should be below 20% moisture content. A piece of dry firewood has large cracks or checks in the end grain. Look for these when judging the quality of firewood. Hardwoods and softwoods are chemically similar—the difference is density. Hardwoods, being more dense produce a longer-lasting fire.

3. Starting or Rekindling the Fire

When starting a fire, use plenty of crumpled newspaper and kindling. As a guide, fill the firebox completely with loosely crumpled newspaper and hold it down with at least ten pieces of finely-split dry kindling. Softwoods make the best kindling. Find out where the combustion air enters the firebox of your stove and light the fire there so that the fire gets plenty of air. Open the air inlets fully.

1. Use dry, split kindling and newspaper to set the fire
2. Use a separate piece of newspaper formed into a torch and lit at one end to warm the flue, once the damper is opened
3. When draft is established, light the kindling
4. Once the kindling is burning, add pieces of larger wood. Be careful not to smother the fire with pieces that are too large
5. Do not overload the firebox
6. Burn fires of reasonable size
7. Do not burn garbage or waste materials, especially highly flammable materials such as gift wrappings or evergreen boughs
8. Never use flammable liquids to start a fire.

Burn Dry Wood Because:

1. It gives up to 25% higher efficiency
2. It produces fewer creosote deposits
3. It ignites faster and smokes less
4. It is lighter to carry
   

Remember:

1. Clear the area around the fireplace and chimney. Debris too close to the fireplace could cause a fire. Check the flue for obstructions like birds' nests, and trim any overhanging branches or large trees near the chimney.
2. Always use a fireplace screen.
3. Never overload the fireplace with too many logs. Don't use the fireplace as an incinerator, and never burn garbage, Christmas trees, or piles of paper.
4. Keep a fire extinguisher on hand and place smoke detectors throughout the house. Test the smoke detectors and batteries regularly. See that the extinguisher is in good working order and that all family members know how to operate it.
5. When building a fire, place logs at the rear of the fireplace, preferably on a grate.
6. Never leave fire unattended. Be sure the fire is extinguished before you go to bed.
7. Keep wood stacked, covered, and out-of-doors, away from the house and off the ground. Bring in only as much as you need for one evening to prevent insects that may be in the wood from entering your home. Manufactured Firelogs, which are packaged to eliminate insects and mess, can also prevent this problem.
8. Have your fireplace inspected annually and cleaned when necessary by a CSIA Certified Chimney sweep. A dirty fireplace can cause chimney fires or contribute to air pollution. Your local CSIA Certified Chimney Sweep will diagnose your fireplace and recommend what it needs in order to burn cleanly and safely.

Think Clean

1. Have your fireplace inspected and cleaned annually by a National Chimney Sweep Guild Certified chimney sweep. A dirty fireplace can cause chimney fires or contribute to air pollution. Your local NCSG-certified chimney sweep will diagnose your fireplace and recommend what it needs in order to burn cleanly and safely.
2. Choose the right fuel. In general, hardwood firewood (oak, madrone, hickory, ash, etc.) burns cleaner than softwood firewood (fir, pine, cedar, etc.). Independent tests (conducted by Shelton Research Labs, Santa Fe, NM) have proven that manufactured firelogs burn much cleaner than firewood.
3. Use seasoned wood, wood with a moisture content of less than 20 percent, burns much cleaner than green (high moisture content) wood. Check with your cordwood supplier to make sure that the wood you purchase is seasoned.
4. Burn smartly. Good fireplace habits can decrease fuel consumption in the home while maintaining the same level of warmth. Make sure the fire gets enough air to burn properly. Close the damper when the fire is out to keep warm room air inside.
5. Minimize creosote buildup which causes chimney fires. Creosote is the black tarry or flaky substance formed in chimneys during the wood burning process. While firewood leaves flammable creosote and carbon deposits on chimney wells, tests show firelogs leave significantly less creosote accumulation than wood.
6. Make a fire that fits your fireplace. A fire that's too large or too hot not only wastes fuel, it can crack your chimney.
7. Keep your fireplace in good working condition. If you notice any cracks in the chimney, and any loose mortar or brick, have your chimney repaired. Have the chimney liner inspected for cracking or deterioration.
8. Read and follow the label when using firelogs. Use one firelog at a time, starting it with a fireplace at room temperature. Don't poke or break manufactured logs. This will cause them to crack apart, releasing their energy at a high rate and resulting in a shorter burn time. Firelogs perform best when burned on a supporting fireplace grate with a maximum of three to four inches of space between support bars.
9. If your fireplace is equipped with glass doors, leave them open while burning a firelog to allow proper draught and cleaner burning. Once you're sure the fire is extinguished, close the damper and glass doors to retain warm air inside the house.