5 Warning Signs Of Creosote Buildup

Creosote is a natural byproduct of burning wood, and a little is normal. The problem is when it builds up faster than it gets cleaned, since it's also highly flammable. Here are the signs worth paying attention to.

1. A strong, sour smell

A noticeable odor from the fireplace, especially in humid weather or when the AC is running, is often creosote off-gassing inside the flue.

2. Visible black flakes or tar-like residue

If you can see shiny, tar-like buildup or black flakes on the damper or firebox walls, that's creosote at a stage that needs professional removal, not a DIY brush.

3. A noticeably slower draft

Smoke backing up into the room more than it used to is often a sign the flue opening has narrowed from buildup.

4. It's been a year (or a cord of wood) since the last sweep

Most guidelines call for cleaning annually or after roughly a cord of burned wood, whichever comes first.

5. You just don't know when it was last swept

If you bought the house and don't have records, it's worth treating that as a sign on its own — better to find a clean flue than assume one.