IPA: /ˈfaɪərʊm/
KK: /ˈfaɪərʊm/
A room or space in a ship or other structure where fuel is stored and burned to generate heat or power.
The crew checked the fireroom to ensure the fuel levels were adequate for the journey.
This word originates from Old English, where 'fire' (meaning the element of combustion) and 'room' (meaning a space or area) combine to describe a space designated for fire, typically used in the context of a fireplace or furnace.
Think of a 'space' ('room') specifically for 'fire' — that's what a fireroom is.