Safety first: Turn off power and gas. Sooting indicates a serious combustion problem and potential carbon monoxide hazard.

Step 1 – Stop operation: Do not operate the boiler until the cause of sooting is identified and corrected.
Step 2 – Check air intake and vent: Ensure both intake and exhaust are clear and properly installed. Remove any obstructions.
Step 3 – Inspect burner and heat exchanger (pro): A technician should remove and clean the burner and inspect the heat exchanger for soot buildup. Heavy soot may require specialized cleaning.
Step 4 – Verify gas settings (pro): Gas pressure, orifice size, and combustion settings must be checked and adjusted with proper instruments.
Step 5 – Combustion analysis (pro): A full combustion test should be performed to confirm safe operation before returning the boiler to service.

Warning: Sooting is a red-flag condition; involve a qualified gas technician immediately.

Boiler’s vent termination shows signs of sooting or black staining.

Possible Causes