Ducts pierce the walls, floors, partitions and ceilings. One such fire in a Nevada hotel resulted in the deaths of 85 people because the central air conditioning system pumped deadly smoke throughout the burning building. There was no smoke detector inside the air conditioning system designed to shut down the system when a fire occurred. So, the first action taken by fire officer in command of a fire inside a fire-resistive building should be to order the air system shut down. Auto-exposure, the vertical spread of flames from windows below to windows above, is another way fire spreads throughout a type I building.
Flames erupting out of a heat-shattered window can melt and break the glass window directly above.
Once the window above is broken and falls away, flames can enter and ignite ceiling tile, curtains or furnishings. Even if the windows do not melt or break from heat, a small-concealed space between the exterior wall and the end of the floor slab can allow vertical spread of fire and smoke from floor to floor above and near a window. To combat fire spread by auto-exposure, the officer in command should order an aerial master stream into operation. A water stream can slow down auto-exposure fire if it is within the reach of the aerial ladder. A water stream directed against the spandrel wall the exterior wall between the top of one window opening and the bottom of the window above can slow down fire spread.