Sauna Stones on a Yacht Producing Smoke or Turning Black

If sauna stones begin to smoke, emit unpleasant odors, or blacken quickly, this is a clear sign that the heater is not operating correctly. On yachts, this issue is particularly common: constant vibrations, salt exposure, long periods of inactivity, and, in some cases, the use of unsuitable stones can alter the normal operation of the system.

To help you understand what is happening and how to intervene, this section lists the most common causes and effective solutions to restore proper sauna function.

 

1. Poor-quality or unsuitable sauna stones

Not all stones are suitable for repeated heating. Using inappropriate stones can cause them to crumble, produce dust on the heater, blacken quickly, or even burn, generating unpleasant odors.

Solution → Use only stones specifically designed for sauna heaters (typically certified peridotite, olivine, or volcanic sauna stones).

 

2. Broken or dusty stones due to yacht vibrations

During navigation, the vibrations and movements of the yacht can cause sauna stones to break.

What happens:

  • stones crumble
  • dust falls onto the heating elements
  • heat circulation is reduced
  • heating elements overheat → causing burning smells and blackened stones

To resolve this issue, it is recommended to remove all stones, replace broken ones, wash them before reinstallation, and restack the stones leaving air gaps to ensure proper heat circulation.

 

3. Stones packed too tightly

If sauna stones are too close together, airflow is restricted and the heating elements may overheat. This manifests as smoke, burning odors, stones blackening quickly, and elements glowing intensely in a short time.

Best practice is to arrange the stones leaving gaps and ventilation channels, especially between the heating elements and the heater casing, to ensure even and safe heating.

 

4. Old or never-replaced stones

On yacht saunas, stones wear out faster than in land-based saunas due to vibrations, marine humidity, salt, and frequent thermal shocks. When stones become too old, they no longer transfer heat effectively and can cause smoke, unpleasant odors, or overheating of the heating elements.

Solution → Replace them completely every 6 months to 1 year.
 

5. Water or moisture residue on the stones

If stones are damp due to seawater, condensation, or internal humidity, the first heating cycle may:

  • produce smoke
  • emit unpleasant odors
  • blacken

What to do? → Thoroughly dry the cabin and never pour seawater onto the stones.
 

6. Overheated or improperly covered heating elements

A heating element that is not properly covered by stones or is bent tends to overheat everything around it. This can cause stone blackening, excessive hot spots, and a metallic burning smell. To prevent this, it is essential to ensure all elements are straight and adequately covered by stones.

 

7. Odors caused by burnt materials inside the sauna

Smoke or unpleasant odors do not always originate from the stones: they may be caused by wood debris, splinters, dust, or other materials that have accidentally fallen into the heater. This issue can be easily resolved by carefully cleaning the heater chamber and removing any residues that could compromise operation and hygiene.

 

When should the sauna be switched off immediately?

It is essential to turn off the sauna immediately if any of the following occurs, requiring expert inspection:

  • smoke becomes intense
  • there is a smell of burnt plastic
  • a heating element glows red in an unusual spot
  • the control display shows errors

 

Centro Italia Yachting - Technical Support and Spare Parts for Yacht Saunas

Centro Italia Yachting provides complete technical assistance and spare parts to ensure the correct operation of saunas and wellness areas onboard yachts. To contact the team, call the toll-free number 800 931 931 from Italy or +39 327 612 0605 from abroad. Alternatively, all requests can also be submitted via the Contact page to receive fast, qualified support from the team.