Fire and life safety in a high-rise

03/01/2009


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A typical building fire begins slowly, as combustible materials are gradually warmed by a heat source to their ignition temperature. The level of fire protection installed within a building and the response of the local fire department will determine whether a fire is controlled or grows into an inferno.

This article will describe the extremely different outcomes of two similar fires in two similar high-rise buildings and will explain why one event became a catastrophe while the other garnered merely a brief mention on the nightly news.

Recipe for disaster

The first fire is the disastrous Feb. 1, 1974, high-rise fire at the 25-story Joelma Building in Sao Paulo, Brazil. This reinforced concrete skyscraper was built from 1969 to 1972. Banco Crefisul occupied most of the building, and the bank offices held a considerable fire load of desks, papers, curtains, carpets, plastic insulation and wall coverings, and wooden walls. The bottom eight stories were occupied by a parking garage. Emergency egress was limited to a single stairwell that was not built as a fireproof enclosure. The building had no fire walls, emergency lighting, fire alarms, fire sprinkler system, fireproof emergency exits, posted evacuation plans, emergency signage, or smoke control system.

The fire began at 8:50 a.m. An air conditioner on the 12th floor overheated and started the fire. The air conditioner circuit required a special circuit breaker that had been omitted because it was not available at the time of installation. The circuit was installed to bypass the electrical control panel on the 12th floor. The lack of this simple protective device allowed the air conditioner motor to overheat and set fire to adjacent materials. Due to combustible products used throughout the building, the fire spread quickly, and the building was engulfed in flames within 20 minutes.

The fire was discovered soon after it started but was initially reported to the Sao Paulo Fire Dept. by a resident of an adjacent building nearly 15 minutes later. The first responding units arrived 5 minutes later and immediately called for backup. The fire crews entering the single stairway were unable to proceed up the stairway beyond the 11th floor, which was the first business office level. The single open stairway burned to the 15th floor and filled the remaining building height with smoke and heat, preventing use as the intended fire escape.

Evacuation

Nearly 300 people were evacuated using the four elevators. The elevator operators were only able to make a few trips before the elevator shafts filled with heat and smoke, making further rescue by elevator impossible.

Lacking a feasible escape path, approximately 170 people sought refuge on the roof. Some reports claim as many as 100 people may have been rescued by helicopters from the top of the burning building.

One extremely brave police officer hastily rigged horizontal ropes to an adjacent building and led 18 occupants to safety on this thin lifeline. Approximately 80 people found shelter under the building roof tiles and were later found to be the lone survivors on the rooftop.

Some fortunate office workers survived by climbing onto ledges or balconies that had sufficient protection from the flames and smoke, primarily in the corners of the building. A few brave occupants lowered themselves from floor to floor using the balconies, past the ascending flames to a level where they could be reached by aerial ladders or were hidden from the rising fire.

Few aerial ladder rescues were made during the fire because the lower building levels accessible to the ladder trucks consisted mainly of a parking structure occupied by vehicles, not people. The fire truck aerial ladders were able to extend only to the lowest occupied floors.

The fire's intense flames heated the concrete walls to very high temperatures. This high heat expanded the air and water vapor inside microscopic bubbles in the concrete, resulting in an explosive spalling of the concrete, sufficient to expose reinforcing steel previously buried a few inches deep. The severe spalling affected significant sections of the exterior walls, joists, and columns.

The building suffered extensive structural damage, yet did not collapse, primarily because the combustible building materials burned quickly and prevented prolonged exposure of the concrete-framed building's support structure to high temperatures. That type of prolonged exposure to extreme heat caused the collapse of the steel-framed Twin Towers of the World Trade Center on Sept. 11, 2001.

The Joelma Building fire began to subside by 10:30 a.m. after having consumed all available combustible material, and was extinguished at 1:30 p.m. After the fire was extinguished, fire crews, police units, and medical teams searched for dazed survivors who finally were able to climb down from the site of their harrowing ordeal. A search initially revealed that 179 people were killed.

Taking a toll

Of the 756 people who were in the building, the death toll is generally reported at 188 to 227 people, and the injury total is reported as high as 345. A number of the survivors later died from extensive injuries after enduring months of extremely painful treatment for burns and ensuing infection.

Although the Joelma Building did not collapse during or after the fire, some structural components were damaged severely and required substantial repair prior to the building's reopening. The building was closed for four years for reconstruction and repair. It is now open and occupied, and has been renamed the Praca da Bandeira (Flag Square).

Brazil has a national fire code, which is a general document. Specific fire safety regulations vary by region and city. Sao Paulo has the most advanced fire code within Brazil. Additional fire safety laws were passed in 1975, 1976, 1978, 1983, 1986, 1994, and 2001 as a result of the Joelma Building fire and other high-rise building fires in Brazil.

Annually, more than 17,000 fires have occurred in high-rise structures greater than six stories in the United States alone, so a high-rise structure fire is hardly the unusual event that most people believe it to be. A high-rise building fire can cause many fatalities, even without a structural collapse such as occurred on Sept. 11, 2001. The 1911 Triangle Shirt Waist Factory fire in New York City (146 killed), the 1946 Winecoff Hotel fire in Atlanta (120 killed), and the 1980 MGM Grand Hotel fire in Las Vegas (87 killed) are examples of other high-rise building fires with large loss of life where the structure did not collapse.

Viva Las Vegas

A recent high-rise hotel fire in Las Vegas has many eerie similarities to the Joelma Building fire. The fire occurred at 5 p.m. on July 14, 2008, in the Bally's Las Vegas Hotel & Casino, which is a 26-story reinforced concrete structure. The hotel was built in 1972 to 1973 and has 2,000 guestrooms. The building has three wings built in a T-shape with one interior and one exterior stairwell at each wing.

The Bally's building is the same structure that was originally involved in the 1980 MGM Grand Hotel fire. In that fire, an electrical fire in the first-floor delicatessen spread quickly to the nearby casino and released dense clouds of toxic smoke that traveled upward into the hotel, killing 61 people on floors 16 to 26. The building was closed for nine months for reconstruction and repair and was retrofitted to the 1981 Las Vegas Retrofit Ordinance , which required major revisions to the previous building and fire codes. See “No gambling on fire ordinances” on page 36.

The smoky 2008 fire began in an overheated air conditioner unit on the 20th floor. The fire was confined to the air conditioner, and the smoke produced was confined to an employee break area. The fire was reported to the Clark County Fire Dept. at 5:01 p.m. The first responding unit arrived at Bally's three minutes later. A total of 21 fire department units responded to the fire. The firefighters used the elevator to access the 18th floor and evacuated floors 18 through 21. Heavy smoke was reported on floor 20. Hotel security located a burnt motor on the ceiling air conditioning unit, power to the unit was disconnected, and the fire department verified the fire was extinguished at 5:17 p.m. A second alarm was cancelled at 5:20 p.m., and the fire department units left the hotel at 5:54 p.m.

A marked difference

Both buildings were concrete-reinforced high-rise structures of nearly identical height. Both buildings were built at approximately the same time period, the early 1970s. The fires in both buildings started in air conditioning units. Both buildings have withstood a major fire without structural collapse.

How could two similar fires in similar buildings have such dissimilar results? Why does one event end in a shocking tragedy while a similar event results only in a business interruption? Is it mere fortune that blesses some building occupants, while condemning others to a horrible death or, at best, a lifetime of loss or pain?

Specifications, standards, and building and fire codes determine the response of a building during a fire, and the survivability of its inhabitants. While the buildings were similar, one building received a major renovation that rendered it far less susceptible to fire damage than the original building.

The foremost building safety improvement of the 1981 Las Vegas Retrofit Ordinance was the requirement for fire sprinklers in high-rise structures of six stories or more. Installation of a retrofit fire sprinkler system at Bally's ensured that the area surrounding the air conditioning motor would not support continuing combustion of a large fire. The August 2008 fire never reached the temperature required to activate the sprinkler system in the break room.

Limits on flame spread of interior finish materials ensured that the overheated motor at Bally's did not set fire to ceiling, wall, or floor furnishings. The Joelma Building was not sprinklered, and neither was the 1980 MGM Grand Hotel's casino area, through which a tremendous flame front roared at an estimated speed of 19 ft/sec.

The building structural steel in the immediate vicinity of the air conditioning unit at Bally's was fireproofed and was, therefore, unaffected by the 2008 fire.

An area smoke detector mounted within 10 ft of the air conditioning unit alarmed soon after onset of the fire and activated audible alarms and visual strobes on the 19th, 20th, and 21st floors (the floor of incident and the floors above and below the floor of incident). This allowed hotel guests in the rooms closest to the break room to quickly evacuate the area of greatest danger. This area detector also activated the alarm at the Fire Command Center and recalled the service elevator for use by the fire department. Early detection of the fire allowed an alarm to be immediately transmitted to the Clark County Fire Dept.

A local power disconnect, required by Section 440 (VII) of the National Electrical Code , allowed a responding maintenance staff member to remove the electrical power flowing to the air conditioner motor and prevent further overheating of the motor. A circuit breaker provided overcurrent protection, although it did not open due to use of the local power disconnect.

Construction of the employee break room as a passive smoke zone, with fire-resistant walls, ceiling, floor, and door—and smoke seals on doors and smoke zone boundary penetrations—confined the smoke to the break area. The smoke control system in the hotel corridor outside the break area was never activated by a corridor area smoke detector. Elevator shafts were built smoke-tight, which allowed the firefighters to use the elevators to quickly access the location of the fire. Automatic doors closed as required to confine smoke to the area of fire origin, and stair pressurization fans blew fresh air into the exit stairwells in the high-rise hotel to prevent any smoke intrusion into these safe exit pathways.

The fire code in effect at the time of the Joelma Building fire in 1974 did not place these requirements on the building owner. The building and fire codes in effect at the time of the MGM Grand fire in 1980 also did not place these requirements on the building owner. The result for each building was a catastrophic fire less than seven years after opening. The single unprotected stairway in the Joelma Building further compromised emergency egress and resulted in many more deaths.

Requirements that protect building occupants from injury or death and also protect the building from significant damage can be found on the design drawings; on the specifications; in applicable building, fire, mechanical, welding, plumbing, and electrical codes; as well as in the building life safety system's O&M and emergency manuals and procedures. In undeveloped countries that do not have or do not enforce these restrictive requirements, a significant loss of life may result from a high-rise fire. Any one of these requirements can mean the difference between life and death during an emergency situation. Fire tragedies are preventable only if all responsible parties comply with the applicable building safety requirements.


Read more about egress strategies in Jeffrey Tubbs' "

Selecting appropriate egress strategies

"


Author Information

Arnold is associate engineer with


No gambling on fire ordinances

The 19 major features of the 1981 Las Vegas Retrofit Ordinance were:

Sprinklers were required for public entertainment assembly areas larger than 5,000 sq ft. Sprinklers were required for rooms and exit corridors in hotel towers more than 55 ft above ground level. Twenty-five percent coverage was required within 15 months of ordinance adoption, 50% coverage was required within 27 months, 75% coverage was required within 40 months, and 100% coverage was required within 48 months.

Smoke control was required for high-rise occupancies above 55 ft, including pressurized exit corridors and enclosed, pressurized stairways.

Emergency lighting to 1 foot candle was required for exit corridors and stairways.

Exit corridors were required to be built from 1-hour fire-resistive materials, and exit stairways were required to be built from fire-resistive materials.

Exit doors were required to be either self-closing or automatic closing in response to a signal from a smoke detector.

Elevator or utility shafts extending higher than two stories were required to be built from fire-resistive materials.

Basement areas larger than 1,500 sq ft or located more than 75 ft from openings were required to be sprinklered.

Illuminated exit signs were required.

Office buildings taller than two stories, hotels and motels taller than two stories with more than 19 guest rooms, and apartments and condominiums taller than two stories with more than 14 dwelling units were required to install a fire alarm system that did not contain a manual delay.

Every hotel/motel guest room and every apartment dwelling unit was required to install a smoke detector.

Hotel/motel guest rooms and apartment dwelling units were required to install an air supply that was not connected to the exit corridor.

Smoke detectors were required to be installed in the ventilating ducts for hotel/motel guest rooms. The detectors were required to shut down the normal ventilation system, sound a voice alarm, and start the smoke control system.

Smoke detectors were required to be installed in elevator lobbies. The detectors were required to prevent the elevator doors from opening on the alarmed floor, automatically return the elevator to the main floor or an alternate floor for further operation under manual control, and close the elevator lobby doors on the alarmed floor.

Signs directing guests to use the exit stairs and not the elevator in an emergency were required to be posted on each elevator and the elevator call station on each floor. Signs indicating floor level and direction of emergency exits were required to be posted on each floor.

Signs that indicate the stairway number were required to be posted in each stairway.

Hotel, office, and residential buildings more than 55 ft above ground level were required to install a public address system.

Interior finish materials were required to be limited in combustibility.

A central reporting location called the fire command center was required to be installed in all hotel/casinos and malls.

Exterior wall openings were required to have flame barriers extending horizontally 30 in. or vertically 36 in. from the floor.



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