Firebox is a chamber onboard a steam vehicle, where the fuel is burned in order to heat up the water inside the boiler. Coal powered fireboxes have a firedoor, which the engineer can keep open while shoveling coal inside. The door should be kept closed whenever possible. Even though its effect on firebox temperature is minimal, keeping the door open can cause blowback when entering tunnels, a reversal of the exhaust flow that can draw fire into the cab and be catastrophic for the crew. Blowback can be prevented by keeping the door closed, or by maintaining intense airflow when entering a tunnel.
Fireboxes is chambers found on {{pll|Steam Overview|steam}} {{pll|Rail Vehicle Types|vehicles}}, where {{pll|Fuel Storage|fuel}} is burned in order to heat up {{pll|Water Storage|water}} inside {{pll|Boiler|boilers}}.
