In a fireplace, the chamber that contains the fire
The cavity in the open face of the fireplace in which the fire is maintained. The firebox leads directly to the fireplace flue. The firebox is constructed of fire or refractory brick set in fireclay or reinforced mortar in traditional masonry fireplaces. The firebox may also be constructed of metal or ceramic-coated metal panels in more modern prefabricated fireplaces. The walls of the firebox are usually slanted towards the living space both to direct smoke up towards the flue and to reflect heat into the room.
The location in a fireplace where the fire is built and contained. The firebox is constructed on the inside of a special kind of brick manufactured for its refractory qualities and its ability to withstand high temperatures.