Refers to an enclosed heating device used for industrial or heating purposes. Can be used for both a furnace and a boiler, depending on context.
The factory furnace melts metal at high temperatures.
The heating of this building is managed by a central boiler.
sunken hearth; sunken fireplace
Compound of 火 (fire) and 炉 (hearth/furnace). The exact historical derivation is uncertain, but the spelling is conventionally associated with a fire-containing heating device.