We've all read and heard the nightmarish details of how the heroic firefighters made their way — step by step — up the overcrowded and under-designed stairways of the World Trade Center towers on 9/11, only to make it about half way up when the towers collapsed. Or the disturbing stories of how numerous physically disabled occupants were left to wait at elevator lobbies, hoping that somehow, someway an elevator cab would come to their rescue. Those in the elevator industry think there must have been a better way.
In response to 9/11 and other more-recent fire-related tragedies, the elevator industry is working with several government agencies and the major building code bodies to create a code-backed plan that would allow elevators to be operated during fires and other disasters for both firefighter access and occupant evacuation. Currently in the development stages, the new code would be elected into the 2006 versions of both the International Building Code and NFPA 5000 as an alternative or supplement to new code currently in the works that mandates wider stairways (55 or 66 inches) for faster, more efficient occupant egress and firefighter ascent.
Studies by the group show that by using elevators, firefighters can get to the point of a fire six times faster than using the stairs. For instance, one study placed a fire on the 35 floor of a 40-story building with a single-zone elevator scheme. "With the old system of sending the fire department up the stairs, it takes in the order of 30 minutes to get people and equipment up and water on the fire," says Richard W. Bukowski, P.E., senior engineer with National Institute of Standards and Technology. "If they use elevators, it takes just five minutes — a huge difference."
Moreover, by using a combination of stairs and elevators to evacuate occupants from tall buildings, evacuation time can be cut by as much as 50%, says Bukowski, citing data from an occupant egress study that took place at the Petronas Towers in Kuala Lumpur, Malaysia.
In March, NIST co-sponsored a workshop on the topic in Atlanta, along with the American Society of Mechanical Engineers, which is responsible for the elevator design code referenced by the national building codes. Other participating organizations include: the International Code Council, National Fire Protection Agency, board members of the Americans with Disabilities Act (ADA), Otis Elevator Co., KONE Corp., Schindler Elevator, ThyssenKrupp Elevator Co., and several industry consultants and fire experts. "We have all the right people at the table, it's a matter of putting it all together," says Bukowski.
The group has closely studied the fire evacuation plans employed by other countries, and is developing a plan for the U.S. that would be both reliable and economically feasible. Bukowski says there are 12 countries that require buildings 30 meters or higher to install firefighter lifts: dedicated, protected elevators for use by the fire department. "These can also be used to provide assistance for people with disabilities," says Bukowski. "But there are no countries that currently have requirements in place for mass occupant evacuation using elevators."
The plan for the U.S. would not call for dedicated firefighter lifts, which Bukowski says are costly to install and maintain. Instead, it would adapt the country's current "phase 1, phase 2" recall protocol for all elevator-equipped buildings. Under this 1970s-era code mandate, all elevators are automatically recalled to the ground floor and taken out of service if fire or smoke is detected in or around the elevator lobbies, shafts, or machine rooms (phase 1). At that point, fire-service personnel can reactivate the elevators under manual control (phase 2).
Under the new plan, one elevator in each bank of cabs would be pre-designated as the fire department access elevator, programmed to go into phase 1 recall "when any detector in the building on the fire alarm system activates, not just the detectors outside the elevator doors and inside the shaft," says Bukowski. "The other elevators would continue to operate as long as none of the lobby and shaft detectors have gone off, because the elevator system isn't really being threatened."
With the assistance of "smart" communication systems — which would inform occupants and emergency personnel the location and severity of the fire, whether the elevators are operating, estimated time of arrival for each cab, and even how many people are in each cab — occupants could then use a combination of stairs and the remaining operating elevators to evacuate the building. In very tall buildings, the procedure would most likely direct occupants to take the stairs downward to the nearest skylobby, and then ride express elevators to the ground.
"Express elevators tend to run faster, have larger cars, and don't stop on many floors," says Bukowski. "There are still some questions that need to be answered, such as concerns over riding an elevator past a fire floor, particularly if it is not a blind shaft."
Other key components of the scheme include:
Enclosed, 1-hr.-fire-rated lobbies on each floor that are pressurized for smoke protection;
Direct access to each lobby from the stairways;
Two-way communication via a fire command center that allows emergency personnel to track and communicate with occupants;
Windows in stairway doors that allow occupants can see whether the stairs or elevator lobbies are overcrowded;
Pressurized hoistways to protect the elevator shafts from smoke; and
The latest smoke and heat detectors that not only provide an alarm, but also transmit data, including temperature and amount of smoke in the area, in real time to the fire command center.
"With these newer devices, the fire department can monitor conditions in all the lobbies, and if they determine, for instance, that the lobby on level 63 is starting to get smoked up, they can notify the people via an intercom system to move down one or two floors using the stairs," says Bukowski.
NIST is working with the major elevator manufacturers to implement its BACnet communications protocol, which will allow elevator controls to communicate with fire-protection and HVAC equipment. "They'll all talk to each other, so if a heat detector fails, for instance, you'll be able to get the temperature of that space by querying the nearest thermostat," says Bukowski.
One obvious application for this new code: historic structures, which often have inadequate stair capacity and cannot be altered without violating preservation standards. "Protected elevators could to take some strain off the stairs," says Bukowski. He says the group is working with the GSA to plan a future installation of a "fire rated" elevator system in one of the agency's historic structures, to serve as a "tech demo."
For more on the use of elevators during fires, visit http://www.nist.gov/el/disasterstudies/wtc/.