creosote build up inside a chimney flue

Creosote Build Up

Originally contributed by • last updated 3/1/2021

Chim Chimmany Chimneys

There is a reason why wood burning stoves and fireplaces are popular features with homeowners, as they can come with many advantages, often providing an efficient and reliable source of heat. But, if you’ve ever owned or operated a wood burning fireplace, you may also be familiar with terms such as creosote or creosote log. That’s because creosote build up in a chimney flue can not only be problematic, it can be potentially hazardous, as well.


When it comes to wood burning stoves and fireplaces, the term creosote refers to the tarry residue that forms on the interior walls of a chimney (or chimney lining) from the smoke and gases cooling and settling. Creosote build up is problematic because it reduces the airflow through the flue, creating conditions that lead to further creosote build up, and causing fireplace inefficiencies. Creosote is also highly flammable and is known to cause chimney fires, leading to structural damage or worse. Additionally, there are also concerns that exposure to creosote can cause health related issues, such as skin and eye irritations.

What Causes Creosote Build Up?

Having a wood burning fireplace inside your home might seem like a good idea but they can quickly become inefficient and dangerous if not properly maintained. When that happens, one of the first problems you may experience is creosote build up. Here’s how you can reduce the conditions for creosote deposits and other potential problems:

  • Burn only dry, well-seasoned wood as it produces less smoke, burns more efficiently, and helps prevent creosote build up in your chimney flue. You can also burn creosote logs (creosote sweeping logs), which help prevent creosote deposits and improve your chimney’s performance.
  • Inspect your chimney annually and hire a professional chimney sweep to clean out your chimney flue. Although there are DIY kits available, a professional chimney cleaning service will be able to identify potential problems.
  • Warm up your chimney flue to reduce the amount of condensation. Burn a small fire for a short period of time to allow the chimney flue to heat up and dry out any moisture build up. This will help prevent ash and smoke from collecting into the moisture and creating deposits.