Warning in Skyscraper Fire
The fire that raged through two stories of a 50-story New York City skyscraper should be regarded as a warning to take a close look at the fire hazards in modern skyscrapers, W. Robert Powers told the New York Chapter of the Society of Fire Protection Engineers.
Powers, secretary of the New York Board of Fire Underwriters and superintendent of its Board of Fire Protection, called fire-resistive buildings misnamed and declared, “Modern buildings contain many more combustible components and finishes than those built in the past. Buildings of this type erected in this plastic age should more correctly be called ‘semi-combustible’.”
Referring to One New York Plaza in Manhattan, with 50 stories and three basement levels, as a “typical modern skyscraper,” Powers said that the fire that raged through the 33rd and 34th floors of this building, took two lives and caused nearly $10 million damage “provided a major full-scale test for new methods of construction.” A guard detected fire in the ceiling of the 33rd floor beneath a telephone equipment room shortly after 5:45 p.m. Feeding on combustible office furniture, the fire rapidly spread. It severely damaged about half of each of the two floors and caused smoke and heat damage on the 35th floor.
Factors in fire spread
In addition to the combustible office furniture, combustible foam insulation in the exterior walls, unprotected openings for air ducts between floors, and electrical and telephone wires were cited by Powers as factors in the fire spread. Also, the air-conditioning system circulated smoke and hot gases throughout the building, necessitating the evacuation of all occupants. Smoke detectors shut off supply fans in the air-conditioning system at 5:50 p.m., but the return air fans continued to operate until about 7:30 p.m., according to a report of the fire published by the New York Board of Fire Underwriters.
The concealed ceiling space on the 33rd floor where the fire was discovered under the 34th floor telephone equipment room contained “a substantial number of exposed cables having insulation of some degree of combustibility,” the report stated. The fire was drawn through the plenum and “probably spread to the exposed polystyrene foam in the south and east” building walls. It is believed that the fire then “emerged from the concealed space via flaming droplets or flaming gases. As the heat involved overstuffed furniture, its progress accelerated because of the amount of combustibles and the flammable gas given off by the foamed polyurethane,” the report continued.
Progress of fire
“Fire was conveyed to the 34rd floor,” the report stated, “through openings into electrical and telephone closets from the concealed spaces, around the air-conditioning flexible ducts where they passed through the floor, through the mail chute, through electrical connections in the floor and probably by the cables themselves. The openings around the air-conditioning ducts created a hazardous situation since the heat and flame passing through these openings melted and ignited the polystyrene insulation in the outer wall.”
The fire temperature, which is believed to have reached 1,500°F, resulted in the twisting and deflection of steel beams on the 33rd floor. (The bases of typist chairs melted.) The steel had been protected with sprayed asbestos fiber. The underwriters’ report indicated that the steel oxidized in transit from England and the asbestos protective coating applied during construction later fell off with the rust scale in many places.
Also, the report explained, insulation was removed where partitions, plumbing and air ducts were installed and where wires scraped beams or clamps had been attached to them.
In his report Powers recommended:
“1. The use of highly flammable foam cushioning should be prohibited . . .
“2. The total fire load of ‘fireresistive’ buildings must be reduced or automatic sprinklers installed throughout . . .
“3. Wire (power and communication) in any part of an air-conditioning system should be encased in metal conduit or ducts . . .
“4. The protection of steel members in a really fire-resistive building must be accomplished by materials that cannot be readily removed or damaged . . .
“5. Vertical flues in exterior walls between the skin and inner walls or partition should be cut off at each floor by a horizontal fire barrier with fire resistance equal to the floor.
New York Daily News photo, John Pedin.
“6. Where openings through floors for air-conditioning ducts are permitted, the duct should go directly to a noncombustible air handling unit containing no combustible material in the duct passage. Openings in the floor should be equipped with a compression-type seal around the duct to provide a positive fire stop.
“7. Wiring connections through floors should be provided with thermal insulation to prevent transmission of heat . .. negating the fire resistance of the floor.
“8. Air-conditioning systems should preferably be restricted to serving only one floor. Since this is contrary to modern practices, an alternate suggestion would be to subdivide the return air plenum by fire stops to restrict fire spread.
“9. Automatic smoke detectors should be provided at each opening in the return air shaft unless the building is sprinklered.
“11. Means should be provided for venting the building during a fire. This may be accomplished by dumping all the return air to the outside if the air shaft has sufficient fire resistance to withstand the exposure and shutters are arranged to prevent the entrance of fire into floors from the shaft. All air movement on the fire floor should be stopped unless under fire department control.
“12. Elevator call buttons should not be of a type that will call an elevator to a floor because of heat, smoke or flames. (Two building guards died when their elevator stopped at the 33rd floor and the doors remained open.)
“13. Pre-fire plans should be drawn up for all buildings. These should include procedures for notifying occupants, calling the fire department, routes of exiting from the various floors and protection of valuable equipment.
“14. Special equipment for fire department use for operating windows, shutters, fans and elevators should be provided and a planned procedure for emergency operation of the air-conditioning system should be formulated.”
New York Daily News photo, Anthony Casale