Pyrolysis is just another word for the darkening of wood from heat scorching, and there’s a lot to potentially lose.
Yes, wood that has been scorched or blackened from high temperatures can potentially pose a fire risk due to spontaneous combustion. When wood is heated to high temperatures, it can undergo chemical changes that release volatile gases and compounds. If the wood is then exposed to oxygen and has not been properly cooled or ventilated, these volatile compounds can mix with air and potentially ignite, leading to spontaneous combustion.
If your sauna walls have darkened over time, there’s a good chance that pyrolysis is setting in.
To prevent the risk of spontaneous combustion, it’s important to:
- Properly Cool the Wood: Allow scorched or heated wood to cool down gradually in a well-ventilated area. Avoid stacking hot or heated wood in confined spaces.
- Ensure Proper Ventilation: Adequate ventilation helps dissipate heat and volatile gases. Avoid storing heated or scorched wood in closed or airtight spaces.
- Monitor Temperatures: Be cautious when handling or storing wood that has been subjected to high temperatures. Use temperature monitoring devices if necessary.
- Replace or sand down your darkened wood: Restoring wood to its original, lighter tone is a way to beat back the potential for spontaneous combuistion..
- Do a lot of Wim Hof breathing. I’m kidding. #5 is build your sauna with proper setbacks to combustibles.
Saunas can burn down. Pyrolysis is one of the top reasons why saunas burn down.

From the author:
Pyrolysis is the heating of wood, which changes the wood’s chemistry and ignition temperature, an oversimplified description of the process. This typically happens over a long period of time, many cycles of heating and cooling at temperatures as low as 200°F can cause pyrolysis to occur.
Randy Williams, Green Building Advisor
Hiding in your chimney stack
It’s one thing to do something about the blackening of your wood paneling around your sauna stove. But there is an even greater concern. Pyrolysis can occur above your hot room ceiling, within the wood surrounding your chimney. When installing your chimney stove pipe, It is critical to follow the setback requirements from the manufacturer. Beyond this, it is highly recommended to inspect the area regularly.
A little Inspector Jacques Clouseau action every year or so is all you’ll need to see if pyrolysis is on its way to potentially spontaneously catch fire. You don’t need a magnifying glass, just a minute of your time with a flashlight and a peak in the rafter cavity. Pink Panther theme music is not necessary.
Saunas can be prone to burning down. The primary reason is combustible materials without proper setbacks. And the telltale sign of this is Pyrolysis, just another word for a lot to potentially lose.