Creosote is what wood smoke leaves on the inside of a flue as it cools. It is combustible, and it is the fuel behind most chimney fires. Sweeps sort it into three stages because each one is removed differently.
Stage 1: soot and flaky deposits
Dry, dark and powdery. A standard brush sweep clears it. This is what a yearly sweep usually finds when wood is dry and fires burn hot.
Stage 2: crunchy, tar-like flakes
Shiny black flakes that cling harder. They form when fires smolder or the flue runs cool. Rotary tools and more passes are usually needed.
Stage 3: glazed creosote
A hard, glassy coating that can run like tar and harden in layers. It does not brush out. It takes specialized removal treatments, and it should be dealt with before the next fire. Our creosote removal add-on starts at $150.
What speeds buildup
- Wet or unseasoned wood
- Low, smoldering fires and a closed-down air supply
- Oversized or exterior flues that run cold
- Wood stoves and inserts burned on low overnight
What to do
Burn dry, seasoned hardwood, give fires enough air, and have the chimney inspected every year. See chimney cleaning for sweep pricing, or book online.