What is the function of induced draft in boiler operation?

• A. Adds fuel to furnace
• B. Preheats combustion air
• C. Feeds water
• D. Removes flue gases and helps maintain furnace draft

Answer: (D)

Induced draft is the fan-driven removal of exhaust gases from the furnace, pulling combustion products through the boiler and out the stack. Its main function is to create negative pressure inside the furnace, which draws the flue gases away from the combustion zone and prevents them from leaking back into the boiler room. This venting helps ensure complete and controlled combustion, protects equipment and personnel from gas leakage, and stabilizes the furnace pressure for safe operation. It works together with the air supply system that provides the necessary combustion air, so the overall draft is carefully balanced. Fuel is supplied by the burner, and water is fed by the feedwater system—these are separate functions, not handled by the induced draft.