Early in the morning of September 9, 1973, a fire occurred in a 30 room, three-story hotel in Bath, Maine. Four people were killed, and 18 others injured, including four firefighters. The fire began with an oil-burning furnace that had originally burned coal. The horizontal connector, the metal pipe that conducted furnace combustion gases to the chimney, was about 18 inches below a zinc plate on the ceiling. The “normal” temperature in the room was quite hot, and this heat had dried out the wood ceiling above the zinc plate. Eventually, a joint in the connector came apart, and hot exhaust gases escaped and ignited the ceiling above the furnace. The fire eventually spread into the lobby, and ignited a couch, which was noticed by a hotel occupant.
Fire quickly spread up open stairways to the second and third floors, eventually, the fire became so intense that a center section of the building collapsed. NFPA members can read the full Fire Journal article for free.