fire box
noun1
The hearth of a metal-forging shop; the forge of a smithy.
2
An enclosed hearth with hatch for refueling that is attached to or built into a boiler that supplies steam for mechanical power.
- The brakeman had to help the fireman shovel coal into the firebox as the engineer coaxed his locomotive up grade.
3
The internal hearth of a furnace, stove, or heater.
4
The hearth of an outdoor grill.
- When the bottom of the grill firebox burned through, everybody ran over and stomped embers too keep the picnic shelter from catching fire.