What is the name of the heated interior of the boiler?

• A. Fire box
• B. Combustion chamber
• C. Boiler room
• D. Furnace

Answer: (A)

The heated interior where the fuel burns inside a boiler is the firebox. This chamber holds the fuel and flame, is built to withstand high temperatures, and sits in the boiler so the heat from combustion can transfer into the water or steam-generating tubes. That direct burning area is what we call the firebox, making it the correct term for the heated interior of the boiler.

While a combustion chamber is a general term for where burning occurs, in boiler terminology the space specifically designed for burning inside the boiler is the firebox. The boiler room is simply the room that houses the boiler, not part of the boiler itself. A furnace refers to the overall heating device, not the interior burner area of a boiler.