Furnace ignites but flame appears yellow and sooty instead of blue and stable

Safety first: Sooty yellow flames indicate unsafe combustion and potential carbon monoxide production. Turn off the furnace and do not operate it until corrected.

Steps:

• Check combustion air: Ensure the combustion air intake is not blocked and that the furnace room has adequate ventilation if using indoor air.
• Inspect burner: With power and gas off, remove and clean the burner head and ports. Do not alter port sizes.
• Do not adjust gas pressure yourself: Gas pressure and air settings must be checked with proper instruments by a qualified technician.
• Schedule service: Have a professional perform a full combustion analysis and cleaning.