Flashover normally occurs at 500 °C or 1,100 °F for ordinary combustibles, and an incident heat flux at floor level of 1.8 Btu/ft²*s. An example of flashover is when a piece of furniture is ignited in a domestic room. The fire involving the initial piece of furniture can produce a layer of hot smoke which spreads across the ceiling in the room. The hot buoyant smoke layer grows in depth, as it is bounded by the walls of the room.