New York F.D. Conducts Fire Tests in High Rise
Wide World photo.
On August 5, 1970, a fire of major proportions occurred in One New York Plaza, a new, 50-story, office building. It spread from the point of origin on the 33rd floor to the 34th floor and involved an area of approximately 20,000 square feet on each floor.
Structural damage was extensive and the contents were almost completely incinerated. Two occupants lost their lives and many others were seriously injured.
The results of this fire were particularly disturbing because high rise buildings are not supposed to allow fire to extend vertically from floor to floor, or horizontally from one compartment to another. Physiological restraints and the limitations of the building fire protection systems preclude the successful control of fires of this magnitude by manual fire fighting.
The analysis of the fire indicated that the rapid development of the fire and its extension were due largely to the building design and the interrelationships of the various building systems. Briefly, the design features and systems that contributed to the fire are as follows:
The central core contains all services and systems, leaving the remainder of the floor area open. This is very attractive from a rental and utilization standpoint. However, the open-floor concept fails to limit the size of the fire in the manner of the well-compartmented high rise structures of preWorld War II construction. Dwarf partitions to the underside of the ceilings subdivide the floor area, but their effectiveness is negated by the common plenum between the ceiling and the upper floor slab.
This open artery, which transfers the return air from the air-conditioned spaces to the return shaft, also interconnects the entire floor area and provides a means of conducting highly heated convected air from the seat of the fire to remote spaces. The air enters the remote space through registers in the ceilings and gradually drops until it contacts combustible contents, which are ignited without the necessity of direct flame contact. The fire department is then confronted with a large-area fire without the benefits of structural elements to assist in the confinement.
In addition, if the fire development is relatively slow for any one of many reasons, the same arteries transfer smoke and carbon monoxide to remote spaces, where they enter through the register and contaminate the atmosphere. Death has resulted from these conditions.
Furthermore, the location of airconditioning system return shafts in the central core causes air currents to flow in this direction. This results in convected heat being concentrated in the vicinity of the open elevator corridors, which are in the core. The heat, smoke and flame can register an unsolicited call on the inductance buttons, which has resulted in occupied elevators stopping at the fire floor and causing the deaths of five persons. In addition, the heat has melted and shorted mechanical buttons with the result that the circuit is closed and the car again responds to the fire floor. Heat has also warped elevator doors, making them inoperative. When they are warped in the open position, the results are often fatal. If warped when closed, the doors provide a temporary shield to allow time for rescue or possible evasive action, such as sliding the cable to a point of safety.
Heat can also destroy the insulation on the wiring of interlocking circuits. When this happens, a circuit shorts, the elevator stops and remains stopped until the wiring is repaired. This has caused elevators containing building occupants or firemen to become stalled between floors, creating an additional problem in effecting their rescue.
The location of stairways in the central core and the air current that is directed toward them by the negative pressure from the return shaft intensifies the contamination of the stairs with the products of combustion generated by the fire. This is a serious problem that threatens life, encourages panic, has resulted in numerous serious injuries and makes evacuation of the building very difficult. In conjunction with the stack action of the stairs, it also complicates the distribution of smoke to the upper floors of the fire building, once again compromising life safety.
The location of services such as power, light and communications in the core makes them unusually susceptible to heat damage because, once again, due to the heat flow toward the core, the damage in the vicinity of the core is generally the greatest.
Finally, the flow of heat toward the core places fire fighters at a disadvantage because their entry via the interior stairs to the Fire floor is at the point of highest heat concentration. Without protective clothing that can properly protect them in heated atmospheres of this intensity, their tactics are frequently defensive with the objective of protecting the area in the vicinity of the core, preventing additional horizontal spread beyond the area of original involvement, and relying on controlled burning and eventual consumption of fuel in the areas beyond the reach of the hose streams.
Central air conditioning
Central air conditioning presupposes a well-insulated building. This means that virtually all of the heat generated by a fire is contained within the building. The return of the air-conditioning system has an air exchange rate of three to four changes per hour, hardly enough to remove the amount of heat generated by a fire. The supply air provides an increased flow of oxygen to the fire, increasing the rate of fire development and heat emission. In conjunction with the insulation and heat distribution effects of the design, this creates the potential for large areas of involvement and tremendous heat development that almost put the fire beyond the range of interior manual fire fighting.
As mentioned above, elevators are adversely affected by heat, smoke and flame. This presents life safety problems as well as increasing the difficulty of gaining access to the upper floors.
Other problems identified were the poor performance of spray-on insulation for steel structural members, which allowed major distortion of
steel components and disruption of flooring, poor fire-stopping design in the exterior walls between the edge of the floor slab and the exterior skin of the building, and other factors that either contributed to the fire spread or added to the fire loading. However, they are not specifically related to the tests to be described and therefore are not covered in detail.
Second fire verifies analysis
As was to be expected following the reporting of the analysis of the contribution of the building design to the development of the fire, there was a wave of criticism and opposition that lasted some three or four months until the occurrence of a second fire.
This fire at 919 Third Avenue involved 7500 square feet of occupied space and was confined to one floor. However, it claimed three lives, and the damage, the characteristics of fire spread, the rate of development and the distribution of the products of combustion all indicated that the initial analysis was correct.
Following this last experience, a Mayor’s Committee on High Rise Buildings was formed and recommendations were drawn in the form of amendments to the New York City Building and Fire Prevention Codes to correct the conditions which contributed to these tragic fires. After a year of deliberation, these recommendations were submitted by Mayor John V. Lindsay to the City Council for action. The committee was composed of members of the city government, consulting engineers, architects, builders, real estate investors, insurance representatives and organized labor.
In the area of smoke control in stairways, the recommendations were based upon the best information available from the work done by Canadians and British. However, it was recognized that this data was limited at best, and therefore a proposal was made to conduct tests in a high rise building, using full-scale fires to test the feasibility of pressurizing stair shafts and also exhausting smoke through a vertical shaft.
City provides test funds
The City of New York, through its program of supporting urban research in private universities, provided $75,000 to fund the project. The New York Board of Fire Underwriters provided an additional $10,000, and the Port of New York Authority allowed us the use of a 22-stoty office building scheduled for demolition. The building was ideally suited for our purposes. Fan installations at both the ground level and the roof were readily made while allowing for effective control of pressurization and exhaust.
The building was originally compartmented under older design concepts, which allowed us to test the effectiveness of compartmentization, while some of the areas had been renovated by removing all the interior partitions, hanging a ceiling to provide a common plenum and then installing central air conditioning. This allowed a comparison of the open-floor concept versus compartmented floor areas.
A contract was entered into by the city with the Brooklyn Polytechnic Institute’s Center for Urban Environment. Dr. Paul D’Cico headed the project, while the actual testing was conducted by Dr. Robert Cresci, whose specialty is low-velocity air movements. Technical assistance in the fire development and suppression area was provided by Battalion Chief Joseph Rooney, Office of the Chief of Department, New York Fire Department. Instrumentation and technical assistance were provided by the National Bureau of Standards. (continued)
Port of New York Authority photos.
The tests were conducted last April 15, 16 and 19. A total of four tests were made. The details of the tests and the initial impressions reached follow. A more detailed report will be published later by Brooklyn Polytechnic Institute.
Test No. 1
Purpose: To generate sufficient heat and smoke from a full-scale fire to determine if pressurization of a stairway is feasible. To open several doors to determine at what point a series of openings will destroy pressurization. To measure the pressures generated by the fire.
Pressurization: Using 18,000 cfm at base of stair shaft.
Fire Area: A room 32 X 58 feet, stocked with wooden desks and chairs and paper to simulate an office occupancy. No air conditioning was operating; two windows were open to provide ventilation. The room had an open ceiling and full partition from floor to ceiling.
Ignition: Paper saturated with approximately 3 to 4 ounces of lighter fluid.
Fire loading: Approximately 6 pounds per square foot.
- Rapid development of fire forced evacuation of the fire area within 2 minutes, due to smoke and heat. Pressure of .2 inches of water column was developed by the fire.
- Pressurization of stairway within 10 feet of fire area was totally effective.
- Opening of approximately four doors on stairway caused loss of effectiveness. The closer to the source the door opening is located, the greater impact on the loss of pressure.
- Draft from pressurized stair is a great advantage in advancing hose lines.
- Opening the door on the pressurized stair caused an increase in the vigor of the flame and the rate of burning.
- Approximately 75 percent of the total of over 10,000 pounds of combustible material was consumed in 35 minutes.
- In spite of the intensity of the fire, there was no extension beyond the area of involvement due to the full partitions.
Test No. 2
Purpose: To test the smoke distribution characteristics of a fire in a space with a common ceiling plenum, with the air-conditioning system—supply and return—in the off position.
Fire area: Area 14 X 17 feet stocked with wooden chairs, desks and paper stock to simulate an office occupancy. Common plenum with air conditioning off.
Ignition: Match to ignite paper.
Fire loading: Approximately 8.5 pounds per square foot.
- Fire development was rapid.
- Smoke generation was strong. Office space 139 feet distant from fire area contaminated with smoke within 10 minutes to the degree that it was not tenable for the layman. Note: This simulated an actual fire which caused one fatality.
- Elevator lobby was heavily charged with smoke, totally obscuring ceiling lights, exit lights and bodies within 3 feet. Elevator capacitance button was actuated by smoke, causing unsolicited response of elevator.
Test No. 3
Purpose: To test the fire spread characteristics of a fire in a room with a common ceiling plenum with the air conditioning on. To determine if heat convected through plenum can enter remote space via ceiling register and ignite combustible materials on desks.
Fire area: A 16 X 10-foot room stocked with wood desks, chairs and papers to simulate office occupancy. Air conditioning supply and return in the on position. Adjacent rooms provided with desks and paper to determine if ignition could be accomplished.
Ignition: Match on paper.
Fire loading: Approximately 10.4 pounds per square foot.
- Fire development more vigorous than in Test No. 2.
- Heat flow towards return of airconditioning system. Highest temperatures in vicinity of core.
- Remote camera recorded the downward progression of blanket of convected heat as defined by the heavy black smoke content. When edge of heat blanket reached paper on desk, ignition occurred and was recorded on camera. This proved our initial theory on part of the propagation mechanism.
- Higher temperatures were reached and there was more complete incineration of combustibles as a result of a greater oxygen supply.
Test No. 4
Purpose: To test the effectiveness of exhausting smoke from a fire area using a negative pressure on a vertical shaft.
Fire area: Same as Test No. 2.
Ignition: Same as Test No. 2.
Fire loading: Same as Test No. 2.
- Smoke was effectively removed via the vertical shaft without allowing contamination of the elevator lobby.