ARC Chimney Guides
What Is Creosote and Why Is It Dangerous?
Creosote is a combustible residue formed when wood smoke cools against the flue walls. It builds in three stages — loose and flaky, hardened and tar-like, and a glazed crust — and Stage 3 creosote is the leading cause of chimney fires.
The short answer
Creosote is the combustible byproduct of burning wood. As smoke rises and cools against the flue walls, its tar and particle content condenses and sticks, building up fire after fire. It accumulates in three stages, each more flammable and harder to remove than the last — and a Stage 3 glaze is the single biggest cause of chimney fires.
The three stages of creosote
| Stage | What it looks like | How it is removed |
|---|---|---|
| Stage 1 | Loose, flaky, dull soot | Brushes out during a standard sweep |
| Stage 2 | Hardened, shiny, tar-like flakes | Rotary or chemical removal |
| Stage 3 | Thick, glazed, dripping crust | Chemical treatment to convert, then remove |
Why creosote forms faster in some chimneys
- Burning unseasoned or wet wood, which smolders and produces cooler, smokier exhaust.
- Slow, damped-down fires that keep flue temperatures low.
- An oversized or exterior chimney with cooler flue surfaces.
- Restricted airflow from a partially closed damper or a dirty flue.
Why it is dangerous
A Stage 3 glaze can ignite at temperatures above 2,000°F. A chimney fire that hot can crack the flue liner, ignite nearby framing, and spread into the home — often burning unseen inside the flue. Any Stage 3 finding also signals the liner may already be compromised and warrants a Level 2 video inspection.
How to prevent creosote buildup
- Burn only dry, seasoned hardwood.
- Keep fires hot and well-ventilated rather than smoldering.
- Have an annual chimney sweep so buildup never progresses past Stage 1.
- Book fire-prevention service before the burn season if you suspect heavier buildup.
For the cleaning schedule that keeps creosote in check, see how often a chimney should be cleaned.
Protect your home
ARC Chimney Sweeps removes Stage 1–3 creosote across Georgia, Florida, Alabama, Louisiana, and Mississippi, including Atlanta, Birmingham, and Baton Rouge. Call (888) 998-2258 or schedule online.
Frequently Asked Questions
- What is creosote?
- Creosote is a tar-like, combustible byproduct of wood combustion. As warm smoke rises and cools against the flue walls, its particles condense and stick, building up over time into a flammable coating.
- What are the three stages of creosote?
- Stage 1 is a loose, flaky, brushable soot. Stage 2 is a hardened, tar-like coating. Stage 3 is a glazed, shiny crust that is highly flammable and very difficult to remove. Each stage is harder to clean than the last.
- How do you get rid of glazed Stage 3 creosote?
- Stage 3 glazed creosote must be treated with a professional chemical product that converts the glaze into a brushable form before it can be removed. It should never be attempted with a standard brush or DIY tools.
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Have a question about your own chimney?
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