Defective Boiler The Importance of Servicing Blocked Flue Poor Combustion Leading to Blocked Heat Exchanger Debris on Burner Poor Combustion Poor Combustion Carbon Monoxide Carbon Monoxide = = Serviced Example Clear Heat Exchanger Clean and Clear Burner and Flue Rope Seals Changed and Fan Checked Burner Pressure Gas Rate Safe Operation Safety Controls Ventilation Flue Termination