Every hotel shall be provided with one fire extinguisher, of style and size approved by the national board of fire underwriters, on each floor containing twenty-five hundred square feet of floor area; and one additional fire extinguisher on each floor for each additional twenty-five hundred square feet of floor area, or fraction thereof. Every such extinguisher shall be placed in a convenient location in the public hallway, outside of sleeping rooms, at or near the head of stairs, and shall always be in condition for use.