A chimney fire is the failure mode of wood heating: creosote — tar condensed on flue walls — ignites and burns at furnace temperatures. The good news is that the prevention chain is short, cheap and entirely in your control.
Where Creosote Comes From
Wood smoke carries unburned volatile gases. When that smoke meets a cool flue surface, the gases condense into creosote — shiny, tar-like, and dangerously flammable in thick deposits. Three things accelerate it: wet wood (extra moisture cools the fire and flue), smouldering fires (low-temperature burns send more unburned gas up the stack), and short, cold chimneys on exterior walls.
Prevention Link 1: Dry Fuel
This is 80% of the job. Below-20% wood burns hot and clean, leaving minimal condensable tar. Every Ember Peak load is meter-tested to that standard — the physics: moisture guide. Burning green wood doesn’t just waste heat; it’s actively painting your flue with fuel.
Prevention Link 2: Hot, Complete Burns
After an overnight low-and-slow session, run the heater briskly for 20–30 minutes to dry out the flue — the “clean burn” habit. Build fires with real airflow (proper lighting sequence), and if your fires smoke routinely, fix that too: the smoke guide.
Prevention Link 3: Annual Sweeping
Even perfect technique deposits some creosote over a season. An annual sweep keeps it thin and harmless — schedule it before the season, as in our first-fire checklist. Between professional visits, a sweep kit (see cleaning products) handles light maintenance on accessible runs.
Warning Signs To Know
- Creosote flakes or tar smell from the fireplace
- Dense smoke backing into the room when the door opens
- A hot chimney smell hours after the fire dies
- Any roaring/flapping noise from the flue — that’s a fire: get out, call emergency services
More safety fundamentals: the fire safety checklist. Fuel that keeps flues clean ships from the firewood shop — and the FAQs cover chimney care in depth.