What Is Creosote — and Why Is It So Dangerous?

Creosote is the tar-like byproduct of burning wood, and it is the number one cause of chimney fires. Here is what every homeowner should know.

How creosote forms

As wood smoke cools on its way up the flue, it condenses into creosote on the chimney walls. Burning unseasoned wood, damping the fire down too far, or an undersized flue all speed up the buildup.

Why it is dangerous

Creosote is highly flammable. Once enough accumulates, a hot fire or stray spark can ignite it, causing a chimney fire that can crack your liner and spread to the home.

How to keep it under control

Burn dry, seasoned wood, keep good airflow, and schedule an annual sweep. A professional sweep removes creosote safely before it becomes a hazard.