High-rise Office Building Fire One Meridian Plaza Philadelphia, Pennsylvania (February 23, 1991)

This fire is a large scale realization of fire risks that have been identified on many previous occasions. The most significant new information from this fire relates to the vulnerability of the systems that were installed to provide electrical power and to support fire suppression efforts. In this incident there was an early loss of normal electrical power, a failure of the emergency generator and a major problem with the standpipe system, each of which contributed to the final outcome. These experiences should cause responsible individuals and agencies to critically reexamine the adequacy of all emergency systems in major buildings.

When the initial news reports of this fire emerged, attention focused on how a modern, fire-resistive high-rise in a major metropolitan city with a well-staffed, well-equipped fire department could be so heavily damaged by fire. The answer is rather simple -- fire departments alone cannot expect or be expected to provide the level of fire protection that modem high-rises demand. The protection must be built-in. This fire was finally stopped when it reached a floor where automatic sprinklers had been installed.

This report will demonstrate that the magnitude of this loss is greater than the sum of the individual problems and failures which produced it. Although problems with emergency power systems, standpipe pressure reducing valves, fire alarm systems, exterior fire spread, and building staff response can be identified, the magnitude of this fire was a result of the manner in which these factors interacted with each other. It was the combination of all of these factors that produced the outcome.

At the time of the One Meridian Plaza fire, the three model fire prevention codes had already adopted recommendations or requirements for abating hazards in existing high-rise buildings. Each of the model building codes contains explicit requirements for fire protection and means

The Fire Department arrived to find a well-developed fire on the 22nd floor, with fire dropping down to the 21st floor through a set of convenience stairs. (For an elevation drawing of the building and the 22nd floor plan see Appendix A.) Heavy smoke had already entered the stairways and the floors immediately above the 22nd. Fire attack was hampered by a complete failure of the building’s electrical system and by inadequate water pressure, caused in part by improperly set pressure reducing valves on standpipe hose outlets.

THE BUILDING

One Meridian Plaza is a 38-story high-rise office building, located at the comer of 15th Street and South Penn Square in the heart of downtown Philadelphia, in an area of high-rise and mid-rise structures. On the east side, the building is attached the 34-story Girard Trust Building and it is surrounded by several other high-rise buildings. The front of the building faces City Hall.

One Meridian Plaza has three underground levels, 36 above ground occupiable floors, two mechanical floors (12 and 38), and two rooftop helipads. The building is rectangular in shape, approximately 243 feet in length by 92 feet in width (approximately 22,400 gross square feet), with roughly 17,000 net usable square feet per floor. (See Appendix A for floor plan.) Site work for construction began in 1968, and the building was completed and approved for occupancy in 1973.

Construction was classified by the Philadelphia Department of Licenses and Inspections as equivalent to BOCA Type 1B construction which requires 3-hour fire rated building columns, 2-hour fire rated horizontal beams and floor/ceiling systems, and l-hour fire rated corridors and tenant separations. Shafts, including stairways, are required to be 2-hour fire rated construction, and roofs must have l-hour fire rated assemblies.

The building frame is structural steel with concrete floors poured over metal decks. All structural steel and floor assemblies were protected with spray-on fireproofing material. The exterior of the building was covered by granite curtain wall panels with glass windows attached to the perimeter floor girders and spandrels.

The building utilizes a central core design, although one side of the core is adjacent to the south exterior wall. The core area is approximately 38 feet wide by 124 feet long and contains two stairways, four banks of elevators, two HVAC supply duct shafts, bathroom utility chases, and telephone and electrical risers.

Stairways

The building has three enclosed stairways of concrete masonry construction. Each stairway services all 38 floors. The locations of the two stairways within the building core shift horizontally three or four times between the ground and the 38th floor to accommodate elevator shafts and machine rooms for the four elevator banks. Both of these stairways are equipped with standpipe risers.

Adjacent to the stairway enclosures are separate utility and HVAC shafts. There are pipe and duct penetrations through the shaft and stairway enclosure walls. The penetrations are unprotected around the sleeved pipes and fire dampers are not installed in WAC ducts penetrating the fire-resistance rated wall assemblies. This effectively creates many openings between the utility shafts, and the individual floors, primarily in the plenum area above the ceilings, as well as between the shafts and the stairway enclosures.

The third enclosed stairway is located at the east end of the building. This stairway attaches the floors of the Meridian Plaza to the corresponding floors of the Girard Trust Building. Adjacent to the east stairway is an additional enclosed utility shaft which also has pipe and duct penetrations through the shaft enclosure walls. There are no fire or smoke barriers around the sleeved pipes and no fire dampers in the HVAC ducts that penetrate the shaft walls.

Elevators

Elevator service is provided by four zoned elevator banks identified as A through D. Elevator Bank A serves floors 2-11. Elevator Bank B has two shafts which enclose seven elevators: six are passenger elevators that serve floors 12-21, and one is a freight elevator that serves floors 22-38. Elevator Bank C serves floors 21-29, and Elevator Bank D serves floors 29-

37. The elevator shafts are constructed of concrete and masonry and extend from the first floor or lower levels to the highest floor served by the individual elevator banks. At the top of each elevator bank is the associated elevator equipment room.

The elevator shafts that serve the upper floors are express rise and do not have openings to the lower floors. Only the Bank C passenger elevators and the freight elevator served the fire floors. The elevator shafts did not appear to play a significant role in the spread of combustion products.

Each elevator lobby is equipped with a smoke detector that, when activated, recalls the elevator cars to the first floor lobby. Firefighter’s service (elevator recall) features were added in 1981 under provisions of

Heating, Ventilation, and Air Conditioning

The heating, ventilation, and air conditioning (HVAC) system is composed of four air handling systems. Two systems are located in the 38th floor mechanical room and service the east and west halves of the upper floors. The other two systems are located in the 12th floor mechanical room and service the east and west halves of the lower floors. Each system supplies air to its respective floors through one or two supply air shafts located within the building core and receives return air from its associated return air shafts. Return air shafts are located at each of the four building comers. Upon examination at selected locations, the HVAC supply and return air shafts did not appear to have fire dampers at the duct penetrations on each floor.

Plumbing

The bathroom utility piping extends through the 38 floors through pipe chases that are formed by the space between two walls. These pipe chases transfer location as the bathroom locations change floor to floor. Upon a sample examination of the pipe chases, it was found that floor penetrations were not closed or sealed to maintain the integrity of the fire-resistance rated floor/ceiling assemblies.

Electrical and Communications Risers

The electrical and telephone risers are enclosed in separate rooms on each floor. The rooms are located directly above one another and are intended to function as vertical shafts, with rated separations required at horizontal penetrations from the shafts into floor and ceiling spaces at each level. Within the telephone and electrical rooms, unprotected penetrations of the floor assemblies allow conduits and exposed wires to travel from floor to floor. Several breaches of fire-resistance rated construction were observed in the walls separating the electrical and telephone rooms from the ceiling plenums and occupied spaces on each floor.

Emergency Power

The building electrical system receives power from two separate electrical substations and is backed-up by an emergency generator. The two sources of power are arranged so that the load would automatically transfer to the second source upon failure of the first. Electrical power for One Meridian Plaza and four adjacent buildings is distributed from the basement of 1414 S. Penn Square.

The electric service enters the building via the basement from the adjoining building and is distributed to the 12th and 38th floor mechanical rooms via the electrical risers in the building core. From the 12th and 38th floor mechanical rooms, electrical power is distributed to the major mechanical systems and to a buss bar riser, which services distribution panels on the individual floors.

Emergency power was provided by a 340 kw natural gas-fired generator located in the 12th floor mechanical room. The generator was sized to supply power for emergency lighting and the fire alarm system, the fire pump located on the 12th floor and one car in each bank of elevators. The generator’s fuel was supplied by the building’s natural gas service. This generator was not required by the building code, since the building’s electrical power was supplied by two separate substations.

The generator was reported to have been tested weekly. The last recorded test date was January 30, almost four weeks before the fire, and the maintenance records indicate that problems were encountered during engine start-up under load conditions at that time. During a detailed inspection following that test, a damaged part was discovered and replaced. After the repair, the generator was started without a load and appeared to work properly, but no subsequent tests were performed to determine if the problems persisted under load conditions.

Records of earlier maintenance and test activity suggest that load tests were performed only occasionally. Test and maintenance records indicate a long history of maintenance problems with the emergency generator system. Many of these problems became manifest during or immediately after conducting tests under load.

At the time of construction, the Philadelphia Building Code required only a local fire alarm system with manual stations at each exit and smoke detectors in the supply and return air shafts. Hose stations supplied from the domestic water service and portable fire extinguishers were required for occupant use. Dry standpipes were installed for fire department use. Below ground levels were required to be provided with automatic sprinklers.

As a result of local code changes, several improvements to the fire protection systems were made in the years following the building’s construction.

In 1981, the Philadelphia Department of Licenses and Inspections implemented amendments to the fire code which were intended to address the life safety of high-rise building occupants. These requirements included installation of stair identification signs, provisions to permit stairway re-entry, and installation of smoke detection in common areas in the path of access to exits. The “common areas” provision of the code was intended to address corridors and exit passageways in multi-tenant floors. The smoke detector requirements were interpreted in such a way that single tenant “open plan” floors were only required to have detectors installed at the exits; the entire floor, although open, was not considered a “common area.” Smoke detectors were also installed in the return air plenum adjacent to the return air shaft intakes in each comer of the building. These provisions required that building owners file permits for this work within one year of the code change. City records do not indicate when this work was performed in this particular building or if it was inspected and approved.

Fire Detection and Alarm Systems

At the time of construction, One Meridian Plaza was equipped with a coded manual fire alarm system with pull stations installed adjacent to each of the three exit stairwells on each floor. Smoke detection was provided in the major supply and return air ducts at the mechanical floor levels.

After the 1981 fire code amendments were! enacted, the hardware on stairway doors was required to allow access from stairs back to floor areas or to be unlocked automatically in the event that the fire alarm was activated. One Meridian Plaza was granted a variance from this provision and generally had unlocked doors every three floors.

Approximately one and a half years before the fire, a public address system was installed throughout the building. This system was operable from the lobby desk and had the capability of addressing floors, stairways, elevator machine rooms, and elevators. Two-way communication was possible with elevators and elevator machine rooms.

As additional devices and systems were installed, they were connected to the fire alarm system to sound through the single-stroke bells originally installed with the manual fire alarm system. Smoke detector and water flow signals were assigned their own codes to allow annunciation not only at the lobby but throughout the building for those members of the building staff who knew the codes.

Standpipes

The occupant use standpipe system, which was connected to the domestic water supply, provided two outlets per floor with 100 feet of 1 l/2-inch hose and a nozzle. The hose cabinets were located in corridors on each floor.

A dry standpipe system was originally installed with 6 inch risers in the west and center stair towers and outlets for 2 l/2 fire department hose lines at each floor level. This system was converted to a wet riser system in 1988, to supply automatic sprinklers on some of the upper floors. An 8 inch water supply was provided to deliver water to two 750 gpm electric fire pumps, one in the basement and one on the 12th floor.

The basement pump supplied the lower standpipe zone (floors B-12) while the 12th floor pump served the upper zone (floors 13-38).

There was no standpipe in the east stair tower.

A November 1988 Board of Building Standards decision permitted both zones to be served by a common fire department connection, as part of a plan that would provide for the installation of automatic sprinklers on all floors by November 1993.2

Due to the height of the zones and the installation of fire pumps, pressures exceeded the 100 psi limit permitted by NFPA 14, Installation of Standpipe and Hose Sytems at the standpipe hose outlets on several lower floors in each zone. Pressure restricting devices, which limit the discharge through standpipe outlets by restricting the orifice, were installed on the mezzanine and second floor levels and on floors 26 through 30. Pressure reducing valves, which regulate both static pressure and discharge pressure under variable flow conditions, were installed on floors 13 through 25.

Both types of devices prevent dangerous discharge pressures from hose outlets at the lower floors of each standpipe zone. The Philadelphia Fire Department investigators report that the plans submitted at the time the standpipes were converted did not indicate that PRVs were to be installed.

Automatic Sprinklers

Only the service floors located below grade were protected by automatic sprinklers at the time of construction. Conversion of the dry standpipe to a wet system with fire pumps facilitated the installation of automatic sprinklers throughout the building. At the request of selected tenants, sprinklers were installed on several floors during renovations, including all of the 30th, 31st, 34th, and 35th floors, and parts of floors 11 and 15. Limited service sprinklers, connected to the domestic water supply system, were installed in part of the 37th floor. The building owners had plans to install sprinklers on additional floors as they were renovated.

Delayed Report

At approximately 2023 hours on February 23,1991, a smoke detector was activated on the 22nd floor of the One Meridian Plaza building. The activated detector is believed to have been located at the entrance to the return air shaft in the northeast comer of the building. At that time there were three people in the building, an engineer and two security guards.’ The alarm sounded throughout the building and elevator cars automatically returned to the lobby. The building engineer investigated the alarm using an elevator on manual control to go to the 22nd floor. The central station monitoring company that served the building reportedly called the guard desk in the lobby to report the alarm. The call came in before the engineer reached the fire floor, and the alarm company was told that the source of the alarm was being investigated. The alarm company did not notify the Fire Department at that time.

When the elevator doors opened at the 22nd floor, the engineer encountered heavy smoke and heat. Unable to reach the buttons or to leave the elevator car to seek an exit, the building engineer became trapped. He was able to use his portable radio to call the security guard at The building staff regulated the after-hours population of the building through a lighting request system where tenants lights would be turned on for the duration of their work. In addition, there was a security system in the building that recorded any passage through stairwell doors. the lobby desk requesting assistance. Following the trapped engineer’s instructions, the security guard in the lobby recalled the elevator to the ground floor using the Phase II firefighter’s safety feature.

The second security guard monitored the radio transmissions while taking a break on the 30th floor. This guard initially mistook the fire alarm for a security alarm believing that he had activated a tenant’s security system while making his rounds. He evacuated the building via the stairs when he heard the building engineer confirm there was a fire on the 22nd floor.

The roving guard reported that as he descended from the 30th floor the stairway was filling with smoke. He reached the ground level and met the engineer and the other security guard on the street in front of the building.

The Philadelphia Fire Department report on the incident states that the lobby guard called the alarm monitoring service to confirm that there was an actual fire in the building when the engineer radioed to her from the 22nd floor. After meeting outside and accounting for each other’s whereabouts the three building personnel realized that they had not yet called the Fire Department.

The first call received by the Philadelphia Fire Department came from a passerby who used a pay telephone near the building to call 911. The caller reported smoke coming from a large building but was unable to provide the exact address. While this call was still in progress, at approximately 2027 hours, a call was received from the alarm monitoring service reporting a fire alarm at One Meridian Plaza.

Initial Response

The Philadelphia Fire Department dispatched the first alarm at 2027 hours consisting of four engine and two ladder companies with two battalion chiefs. The first arriving unit, Engine 43, reported heavy smoke with fire showing from one window at approximately the mid-section of the building at 2031 hours. A security guard told the first arriving battalion chief that the fire was on the 22nd floor. Battalion Chief 5 ordered a second alarm at 2033 hours.

While one battalion chief assumed command of the incident at the lobby level, the other battalion chief organized an attack team to go up to the fire floor. (The Philadelphia Fire Department’s “High-rise Emergency Procedures” Operation Procedure 33 is presented in Appendix C.) The battalion chief directed the attack team to take the low-rise elevators up the 11th floor and walk up from there.

Electrical Power Failure

Shortly after the battalion chief and the attack team reached the 11th floor there was a total loss of electrical power in the building. This resulted when intense heat from the fire floor penetrated the electrical room enclosure. The heat caused the cable insulation to melt resulting in a &ad short between the conductor and the conduit in both the primary and secondary power feeds, and the loss of both commercial power sources. The emergency generator should have activated automatically, but it failed to produce electric power. These events left the entire building without electricity for the duration of the incident in spite of several efforts to restore commercial power and to obtain power from the generator.

This total power failure had a major impact on the firefighting operations. The lack of lighting made it necessary for firefighters to carry out suppression operations in complete darkness using only battery powered lights. Since there was no power to operate elevators, firefighters were forced to hand carry all suppression equipment including SCBA replacement cylinders up the stairs to the staging area that was established on the 20th floor. In addition, personnel had to climb at least 20 floors to relieve fellow firefighters and attack crews increasing the time required for relief forces to arrive. This was a problem for the duration of the incident as each relief crew was already tired from the long climb before they could take over suppression duties from the crews that were previously committed.

Initial Attack

As the initial attack crews made their way toward the 22nd floor they began to encounter smoke in the stairway. At the 22nd floor they found the west stair tower door locked. The door was already warped and blistering from the heat, and heavy fire could be seen through the door’s wire glass window. A 1 3/4-inch hand line was stretched up the stairway from a standpipe connection on the floor below and operated through the window while a ladder company worked on forcing open the door.It took several minutes before the door could be forced open and an attempt could be made to advance onto the fire floor with the 13/4-inch attack line. The crews were not able to penetrate onto the 22nd floor due to the intense heat and low water pressure they were able to obtain from their hose line. An entry was also made on the 21st floor where the firefighters were able to see fire on the floor above through the open convenience stair. They attempted to use an occupant hose line to attack the fire but could not obtain water from that outlet. They then connected a 1 3/4 inch attack line to the standpipe outlet in the stairway, but they could not obtain sufficient pressure to attack the flames. A Tactical Command Post was established on the 21st floor and a staging area was set up on floor 20.

Fire Development

By this time fire was visible from several windows on the 22nd floor and crews outside were evacuating the area around the building and hooking up supply lines to the building’s standpipe connections. As flames broke through several more windows around a major portion of the fire floor, the floor above was subject to autoexposure from flames lapping up the side of the building. Additional alarms were called to bring personnel and equipment to the scene for a large scale fire suppression operation.

As the fire developed on the 22nd floor, smoke, heat, and toxic gases began moving through the building. Vertical fire extension resulted from unprotected openings in floor and shaft assemblies, failure of fire-resistance rated floor assemblies, and the lapping of flames through windows on the outside of the building.

Water Supply Problems

The normal attack hose lines used by the Philadelphia Fire Department incorporate 1 3/4-inch hose lines with automatic fog nozzles designed to provide variable gallonage at 100 psi nozzle pressure. The pressure reducing valves in the standpipe outlets provided less than 60 psi discharge pressure, which was insufficient to develop effective fire streams. The pressure reducing values (PRVs) were field adjustable using a special tool. However, not until several hours into the fire did a technician knowledgeable in the adjustment technique arrive at the fire scene and adjust the pressure on several of the PRVs in the stairways.

When the PRVs were originally installed, the pressure settings were improperly adjusted. Index values marked on the valves did not correspond directly to discharge pressures. To perform adjustments the factory and field personnel had to refer to tables in printed installation instructions to determine the proper setting for each floor level.4 For more detailed information about PRVs see Appendices D and E.

Several fire department pumpers were connected to the Fire Department connections to the standpipe system in an attempt to increase the water pressure. The improperly set PRVs effectively prevented the increased pressure in the standpipes from being discharged through the valves. The limited water supply prevented significant progress in fighting the fire and limited interior forces to operating from defensive positions in the stairwells. During the next hour the fire spread to the 23rd and 24th floors primarily through autoexposure, while firefighters were unable to make entry onto these floors due to deteriorating heat and smoke conditions and the lack of water pressure in their hose lines. Windows on the 22nd floor broke out and the 23rd and 24th floor windows were subject to autoexposure from flames lapping up the sides of the building.

On the street below pedestrians were cleared from the area because of falling glass and debris as more and more windows were broken out by the fire. Additional hose lines were connected to the standpipe connections, attempting to boost the water pressure in the system. However, the design of the PRVs did not allow the higher pressures to reach the interior hose streams. Additional alarms were requested to bring a five-alarm assignment to the scene.

Three Firefighters Lost

As firefighters attempted to make entry to the burning floors from the stairways, heavy smoke continued to build up within the stair shafts and banked down from the upper floors. An engine company was assigned to attempt to open a door or hatch to ventilate the stairways at the roof level to allow the smoke and heat to escape. A Captain and two firefighters from Engine 11 started up the center stair from the 22nd floor with this assignment. Engine 11 subsequently radioed that they had left the stairway and were disoriented in heavy smoke on the 30th floor. Attempts were made to direct the crew by radio to one of the other stairways.

Shortly thereafter a radio message was received at the Command Post from Engine 11’s Captain requesting permission to break a window for ventilation. This was followed moments later by a message from a crew

The pressure reducing valves in the vicinity of the fire floor (floors 18 through 20) were set at “80” on the valve index which corresponded to a discharge pressure between 55 and 57 psi, depending on the elevation. This would provide a nozzle pressure of 40 to 45 psi at the end of a 150 to 200 foot hose line. member of Engine 11 reporting that “the Captain is down.” Approval was given to break the window and rescue efforts were initiated to search for the crew. Search teams were sent from below and a helicopter was requested to land a team on the roof. The search teams were able to reach the 30th floor, which was enveloped in heavy smoke, but were unable to find the missing firefighters. They then searched the floors above without success. An eight member search team became disoriented and ran out of air in the mechanical area on the 38th floor, while trying to find an exit to the roof. They were rescued by the team that had landed on the roof and were transported back to ground level by the helicopter.

Several attempts were made to continue the search, until helicopter operations on the rooftop had to be suspended due to the poor visibility and the thermal drafts caused by the heat of the fire. The helicopter crew then attempted an exterior search, using the helicopter’s searchlight, and at 0117 located a broken window on the southeast comer of the 28th floor, in an area that could not be seen from any of the surrounding streets. Another rescue team was assembled and finally located the three missing member just inside the broken window on the 28th floor at approximately 0215. At that time the fire was burning on the 24th and 25th floors and extending to the 26th.

The victims were removed to the Medical Triage Area on the 20th floor, but resuscitation efforts were unsuccessful and they were pronounced dead at the scene. An estimated three to four hours had elapsed since they had reported that they were in trouble and all had succumbed to smoke inhalation.’

The three deceased members of Engine Company 11 were Captain David P. Holcombe (age 52), Firefighter Phyllis McAllister (43), and Firefighter James A. Chappell (29).

Prior to being assigned to this task, the crew had walked up to the fire area wearing their full protective clothing and SCBAs and carrying extra equipment. It is believed that they started out with full SCBA cylinders, but it is not known if they became disoriented from the heavy

5 The exact time that Engine 11 was assigned to attempt ventilation and the time the crew reported they were in trouble are not known, since the tactical radio channel they were using is not recorded and detailed time records of this event were not maintained during the incident. Estimates from individuals who were involved suggest that the assignment was made between 2130 and 2200 hours and search efforts were initiated between 2200 and 2230 hours. The bodies were located at approximately 0215 hours. smoke in the stairway, encountered trouble with heat build-up, or were exhausted by the effort of climbing 28 floors. Some combination of these factors could have caused their predicament. Unfortunately, even after breaking the window they did not find relief from the smoke conditions which were extremely heavy in that part of the building.

Continuing Efforts to Improve Water Supply

Because of the difficulty in obtaining an adequate water supply, a decision was made to stretch 5-inch lines up the stairs to supply interior attack lines. The first line was stretched up the west (#l) stairwell to the 24th floor level and was operational by 0215, approximately six hours into the fire. At 0221, a 12th alarm was sounded to stretch a second line, in the center (#2) stair. At 0455, a third 5-inch line was ordered stretched, in the east (#3) stair. The operation in the east stair was discontinued at the 17th /floor level at 0600. While the 5-inch lines were being stretched, a sprinkler contractor arrived at the scene and began manually adjusted the pressure reducing valves on the standpipe connections. This improved the discharge pressure in the hoses supplied by the standpipe system, finally providing normal handline streams for the interior fire suppression crews. At this point, however, the fire involved several floors and could not be contained with manual hose streams.

Firefighting Operations Suspended

All interior firefighting efforts were halted after almost 11 hours of uninterrupted fire in the building. Consultation with a structural engineer and structural damage observed by units operating in the building led to the belief that there was a possibility of a pancake structural collapse of the fire damaged floors. Bearing this risk in mind along with the loss of three personnel and the lack of progress against the fire despite having secured adequate water pressure and flow for interior fire streams, an order was given to evacuate the building at 0700 on February 24. At the time of the evacuation, the fire appeared to be under control on the 22nd though 24th floors. It continued to bum on floors 25 and 26 and was spreading upward. There was a heavy smoke condition throughout most of the upper floors. The evacuation was completed by 0730.

After evacuating the building, portable master streams directed at the fire building from several exposures, including the Girard Building #l and One Centre Plaza, across the street to the west were the only firefighting efforts left in place.

Fire Stopped

The fire was stopped when it reached the 30th floor, which was protected by automatic sprinklers. As the fire ignited in different points this floor level through the floor assembly and by autoexposure through the windows, 10 sprinkler heads activated and the fires were extinguished at each point of penetration. The vertical spread of the fire was stopped solely by the action of the automatic sprinkler system, which was being supplied by Fire Department pumpers. The 30th floor was not heavily damaged by fire, and most contents were salvageable. The fire was declared under control at 3:Ol p.m., February 24, 1991.

Smoke Movement

The heated products of combustion from a fire have a natural buoyancy, which causes them to accumulate in the upper levels of a structure. In a high-rise building the stairways, elevator shafts, and utility shafts are natural paths for the upward migration of heated products of combustion.

Stack effect is a natural phenomenon affecting air movement in tall buildings. It is characterized by a draft from the lower levels to the upper levels, with the magnitude of the draft influenced by the height of the building, the degree of air-tightness of exterior walls of the building, and temperature differential between inside and outside air.6 This effect was particularly strong on the night of the fire due to the cold outside temperature. Interior air leakage rates, through shaft walls and openings, also modulate the rate of air flow due to stack effect. Smoke and toxic gases become entrained in this normal air movement during a fire and are carried upward, entering shafts through loose building construction or pipe and duct penetrations. The air flow carries smoke and gases to the upper portions of the structure where the leakage is outward.

At the upper portions of the structure, smoke and toxic gases fill the floors from the top floor down toward the fire, creating a dangerous environment for building occupants and firefighters. During the investigation of this fire, this upward flow was evidenced by the presence of heavy soot in the 38th floor mechanical room and all the upper floors of the building. The path of smoke travel to the upper floors was vividly evidenced by the soot remnants in HVAC shafts, utility chases, return air shafts, and exhaust ducts.

Fuel Loading

Fuel loading on the fire floors consisted mainly of files and papers associated with securities trading and management consulting. At least one floor had a significant load of computer and electronic equipment. In some cases, correlation could be found between heavy fuel load and damage to structural members in the affected area. From the 22nd floor to the 29th floor, the fire consumed all available combustible materials with the exception of a small area at the east end of the 24th floor.

Structural Conditions Observed

Prior to deciding to evacuate the building, firefighters noticed significant structural displacement occurring in the stair enclosures. A command officer indicated that cracks large enough to place a man’s fist through developed at one point. One of the granite exterior wall panels on the east stair enclosure was dislodged by the thermal expansion of the steel framing behind it. After the fire, there was evident significant structural damage to horizontal steel members and floor sections on most of the fire damaged floors. Beams and girders sagged and twisted -- some as much as three feet --under severe fire exposures, and fissures developed in the reinforced concrete floor assemblies in many places. Despite this extraordinary exposure, the columns continued to support their loads without obvious damage

Perhaps the most striking lesson to be learned from the One Meridian Plaza high-rise fire is what can happen when everything goes wrong. Major failures occurred in nearly all fire protection systems. Each of these failures helped produce a disaster. The responsibility for allowing these circumstances to transpire can be widely shared, even by those not directly associated with the events on and before February 23, 1991.

To prevent another disaster like One Meridian Plaza requires learning the lessons it can provide. The consequences of this incident are already being felt throughout the fire protection community. Major code changes have already been enacted in Philadelphia (see Appendix G) and new proposals are under consideration by the model code organizations. These changes may eventually reduce the likelihood of such a disaster in many communities.