Chimney fires can start when creosote—a combustible residue inside the flue—ignites from heat or an ember. In wood-burning fireplaces and stoves, creosote forms as wood-burning byproducts cool and collect on the flue’s inner surfaces.
Reducing the risk means combining fuel and burning choices that help limit new creosote buildup with chimney maintenance. Professional inspection and removal of accumulated deposits when needed are important parts of prevention.
Why creosote buildup can lead to a chimney fire
Creosote is a combustible residue that collects inside the flue—the passage that carries smoke through the chimney. When wood burns incompletely, some combustion byproducts travel upward with the smoke instead of burning in the fire. As those byproducts reach cooler flue surfaces, they can condense and stick to the walls, forming deposits that accumulate over repeated use.
Formation and ignition are separate steps. Creosote buildup leaves combustible material inside the chimney; sufficient heat or a hot ember can then ignite it. At that point, the deposit itself becomes fuel for a fire in the flue.
Burning habits that help prevent chimney fires
|
Habit |
How it affects risk |
Better choice |
|
Burning wet or unseasoned wood |
Wet wood can smolder and promote faster creosote buildup. |
Choose dry, seasoned firewood. |
|
Deliberately keeping a fire air-starved and smoldering |
Too little combustion air can lead to incomplete combustion and more deposits in the flue. |
Avoid prolonging a burn by deliberately starving the fire of air. |
|
Burning household waste or treated or painted lumber |
These unsuitable fuels add avoidable burning hazards compared with firewood. |
Keep these materials out of your fireplace or stove; use firewood instead. |
Chimney maintenance: inspections, cleaning, and blockages
Have your chimney professionally inspected each year. Fuel and burning choices help limit new deposits, but they do not replace maintenance for creosote already in the flue.
Inspection and cleaning are different tasks. Having the chimney checked does not itself remove accumulated creosote; cleaning or sweeping addresses deposit removal. Do not assume that one annual cleaning is sufficient for every wood-burning fireplace or stove.
Blockages create another hazard. Dry nesting material, leaves, and other combustible debris can obstruct the flue and ignite if a hot ember reaches them. This is a separate concern from creosote buildup, so maintenance needs to account for both deposits and obstructions.
When arranging an inspection, ask the chimney professional whether cleaning is needed, when it should be done, and whether any combustible obstructions need attention.