The long-held belief that elevators in skyscrapers should not be used in evacuations during emergencies, particularly fires, is getting another look amid new research into how the World Trade Center towers collapsed on Sept. 11.
"Yes, the country is exploring the idea of using elevators in evacuations," said Dennis S. Mileti, a professor emeritus at the University of Colorado and a member of a special National Institute of Standards and Technology panel that studied the evacuation of the trade center.
Smoky conditions, power failure, malfunctioning heat sensitive door buttons and electric eyes were all things safety experts feared could make elevators death traps.
"Don't use elevators in fires is one of the most successful public education [safety] campaigns in history," added Jason D. Averill, an expert on fire safety for NIST.
But in the wake of catastrophic loss of life on 9/11 and a growing trend toward taller buildings around the world, the role of elevators in mass evacuations, especially fires, is getting serious consideration.
Just how serious is shown by recent actions by two major national organizations involved in building safety. Both the National Fire Protection Association, which provides model fire codes, and the American Society of Mechanical Engineers, which develops engineering standards, have prepared or are proposing standards for the use of elevators in high-rise evacuations.
Hundreds of fire and engineering experts are expected to attend an ASME conference in December focusing on using elevators in fires and other emergencies.
Already, skyscrapers in Malaysia, Taiwan and Dubai -- site of the world's tallest building at 2,717 feet -- are using the concept of elevator evacuations while the 82-story Shard tower under construction in London also plans to do so, said Averill.
While officials at the Port Authority were guarded in remarks about the role of elevators in emergencies, a spokesman strongly suggested they are being considered in the overall evacuation plans for the new Tower One at Ground Zero.
"I would say we are giving consideration to every aspect of the building that would include life safety consideration," said Stephen Sigmund, a spokesman for the Port Authority when asked if the agency is considering elevators in evacuation procedures. He wouldn't comment further.
WTC disaster studied
The push toward elevators comes after years of analysis of the Twin Towers showed how inadequate stairs were, said Edwin Galea, a professor at the University of Greenwich in England.
All three tightly bunched and poorly protected emergency stairways in Tower One were cut at the point of impact by American Airlines Flight 11 from the 93rd to 99th floors. A computer simulation by Galea's staff showed that had just one staircase survived, everyone trapped above the impact could have escaped.
Although elevators in both towers were disabled in the attack, a NIST study of the South Tower found that in the 16 minutes before that structure was hit by United Airlines Flight 175, an estimated 3,000 people safely evacuated using the elevators.
"The [World Trade Center] incident was a wake-up call on the difficulty of undertaking full building evacuations for high-rise and super-high-rise buildings," said Galea.
As a result of its four-year study of the trade center collapse, NIST has made a number of recommendations to ensure buildings can be evacuated in emergencies such as earthquakes, tornadoes, fires or terrorist attacks. Among them are calls to strengthen elevator shafts and stairways, including making sure stairwells aren't clustered. NIST also recommended that consideration be given to "protected/hardened elevators."
Since then, independent engineering and building code groups have formed task forces to come up with model building codes, which local jurisdictions can voluntarily adopt for new construction. NFPA's life safety code published in 2009 says elevators should be in "noncombustible hoistways" with fire resistance shafts separated from the building, and have power supplies that won't cut out when sprinklers are used. A revision set to take effect in 2012 mandates evacuation training, electronic signs to indicate waiting time and emergency centers that can override normal elevator operation.
Elevator industry officials back the emerging standards.
"My organization feels that our products can easily be used safely to get people out of buildings, but are ancillary to all required exits," said Brian Black, a safety consultant for the National Elevator Industry Inc., a trade group.
But permitting elevator evacuations is not the same thing as requiring them, noted professor Norman Groner of John Jay College, who also worked on the NIST study. One of the model codes, the International Building Code, now has provisions that allow elevators for building evacuations if certain design features and precautions have been incorporated, said Averill. Among the measures: enclosed elevator lobbies protected from fire and smoke; shafts shielded from heat, smoke and water; good two-way communication with a command center; and the ability to take an elevator out of service if it is unsafe, said Averill.
Another IBC provision calls for the disabled to have priority in elevator evacuations, he said. That is crucial because Galea and other researchers noted that many disabled people perished in the towers because it wasn't possible to get them down stairways choked with people and firefighters.
Codes set by cities, states
Because there is no federal building code, it is up to states and cities to come up with their own requirements. New York City requires all new high-rise construction to include impact-resistant fire stairs and spacing stairwells placed away from each other. The emergency stair requirements were among a number of major building code changes signed into law by Mayor Michael Bloomberg in 2004, said Assistant Commissioner James Colgate of the city Department of Buildings.
The city building code now also requires hardened elevator shafts and vestibules where people can wait during evacuations.
Today, while the Port Authority is not covered by the city building code, the new Tower One is being constructed with the city's tougher construction requirements in mind, including those for emergency stairs, said Sigmund, the PA spokesman.
"We conform to the building code and try to exceed it and are doing so in this building," said Sigmund.
Sigmund said the elevator shafts will be within a steel core, which itself is to be shielded by a 3-foot-thick concrete core. He said stairways will also be separated by the required distance, which under the city code would amount to one-third of the diagonal of a building footprint.
FDNY Chief Richard Tobin said the department still instructs people not to take elevators in fires unless emergency workers determine otherwise. The emerging safety standards also don't do away with the so-called "phase one" condition, in which elevators go automatically to the ground floor when smoke is detected in the shaft, lobbies or machine rooms, noted Black, something he said doesn't happen often. But officials agree that in the post-Sept. 11 environment, as new technology emerges, elevators are being considered for greater roles in mass high-rise evacuations in some situations.