The inner chamber at the rear of a steam locomotive boiler where coal, oil, or wood is burned. It is surrounded by a water jacket to capture radiant heat and protect the steel plates from melting. The intense heat generated here is drawn forward through the boiler tubes to produce the steam that powers the cylinders.
Heard on the job
The boiler inspector found a cracked staybolt inside the firebox.
Insider tip
The design and size of the firebox dictate the locomotive's overall power output, as it limits how much fuel can be burned at once.