ESCAPE FROM LARGE BURNING BUILDINGS
Most 19th-century cities experienced a great influx of immigrants. Housing abandoned by the rich served as residential housing for the poor. New York City, for one, required a huge number of multiple dwellings. No consideration was given to the fire hazards of these buildings. Hundreds of people lived in what were essentially enlarged private dwellings divided up into many apartments. Terrible multiple fire deaths occurred in these buildings.
Finally, new laws requiring fire escapes were enacted. Some were balconies across the front of adjacent buildings, or horizontal escapes. Others were steel balconies connected by a vertical ladder that passed through an opening in the balconies. As escapes these were fit only for acrobats.
New York’s Tenement House Act of 1903 pioneered many code requirements designed to make combustible multiple dwellings safe enough for occupants to escape. Until World War 11 there was no loss of life from fire in such buildings. Probably the most important requirement was for enclosed, noncombustible stairways with self-closing metal doors on all apartments. Fire escapes of the stairway type, rather than the traditional vertical ladder, were required from each apartment.
Fire escapes also were provided on industrial and commercial buildings and hotels. Until recently, Texas had a very detailed fire escape law that provided outside fire escapes on 30-plus-story high-rises, such as the Texas building in Fort Worth. A trip down such a fire escape would no doubt be terrifying but still would be preferable to an interior stairway polluted with toxic smoke. In some cases chutes and circular slides were provided. Hotels often had a rope in each room. As it became clear that firefighters could not operate from the same stairway that was being used by escaping occupants, a series of platforms up the face of the building connected by a vertical ladder was equipped with a dry standpipe. This was for fire attack. A separate fire escape was provided for evacuation. Unfortunately this excellent concept was lost. Firefighters coming up a stairway to a high-rise fire often are blocked by occupants coming down.
(All photos by author.)
Some intelligent person came up with the idea of placing the exterior fire escape in a fire-resistive enclosure accessible by a balcony or bridge that provided an atmospheric break between the exit door from the floor and the entrance door to the stairway. This came to be called the New York or Philadelphia fire tower, or the smokeproof fire tower. Unfortunately the fire tower was not used for ordinary movement from floor to floor so was often ignored when evacuation was necessary. It usually was not used for fire department attack.
Many developers soon realized that the exterior of the building was premium rent space and the smokeproof fire tow er did not fit into their plans. However, some buildings were built with an interior fire tower in which a smoke shaft w as situated adjacent to a stairway, with an enclosed vestibule between the two. The theory was that the smoke entering the vestibule air space would go up the shaft, leaving the stairway free. However, smoke and heat cannot be separated. The shaft can become a chimney. At a spectacular high-rise fire on Park Avenue in New York City, the aluminum guard railings on the shaft melted, exposing firefighters to the hazard of falling into the shaft. Check shaft rails in your high-rises for aluminum.
The evolution of high-rise evacuation methods continues. In some cases the stairways are simply enclosed, with no ventilation. In the worst cases scissor stairs (two stairways in the same shaft) are provided as alleged “separate exits.” As the extreme danger of these stairways was recognized, forced ventilation was provided for some stairways. The overpressurization of the stairway is supposed to keep smoke from the fire floor from entering the stairway. The pressurized stairway should be reserved for evacuation.
The best exits arc horizontal. Once people pass through the barrier wall, they can evacuate at leisure. A real problem with such exits is that the integrity of the divisions and the operation of the barrier doors are both liable to be compromised. All levels of management must understand the function and be alert to any compromise, no matter how temporary that compromise may be. The absolute ideal would be high-rise towers in pairs with bridges open to the atmosphere connecting the two Structures.
Short of adequate horizontal exits the exterior, smokeproof tower with an atmospheric break remains by far the best exit from a high-rise.
There have been numerous attempts at finding the best way to keep the smoke and heat away from the occupants long enough for them to exit the building. Smoke control using the air-conditioning system was advanced as a cheap and sophisticated method of controlling the smoke. One advocate declaimed, “You may ask, What are the problems? Let it burn, but let it burn clean. Get the people out, then worry about the smoke control systems. When the fire department arrives on the scene they can take over manual control of these systems but these systems are conceived to operate automatically upon detection in the return air ducts and this system is primarily designed to provide life safety in the first five minutes.” (J. Brooks Semple, “Smoke, the Unseen Killer,” IAFC Metropolitan Workshop; Cleveland, Ohio, September 12, 1972.)
Note the catch phrase, “Let the fire burn clean,” as if toxic smoke is not produced by a “clean-burning” fire and the heat is to be disregarded.
There is no such thing as a cleanburning fire in ordinary combustibles. All around the fire combustible materials are being degraded into toxic gases. Elmer Chapman, a former division commander in New York City’s high-rise-loaded midtown and a recognized expert on smoke control and HVAC systems, tells about a high-rise on Seventh Avenue in 1974. (See “Eire Department Perspective on Smoke Control, Part 1,” Eire Engineering, September 1985. Part 2 was published in Fire Engineering the following month.) The automatic smoke control system drew the smoke and fire through the return plenum, a void above the ceramic tile ceiling. The ceramic tiles became red hot, fell, and spread the fire for 200 feet. Despite this, NFPA Standard 92A permits the supply and exhaust of air before the application of any extinguishing agent. This can be extremely dangerous.
The way to solve the smoke problem is not to let it be generated in quantity. This is accomplished by full automatic sprinkler protection, which suppresses the fire shortly after it starts. No arguments can overcome this proven fact. Any unsprinklered high-rise office building is a potential mass death trap.
