for 12/12/07

To read
our previous
ME Online Exclusives,
click here.

Rethinking the
High-Rise Elevator

Two ASME task groups are studying possible revisions to the standards that could change the way people move through large structures during emergencies.

It is a standing rule in buildings that, if the fire alarm goes off, you don’t use the elevators. The cars return to the ground floor where they remain available for use at the discretion of firefighters.

During a fire drill, the fire marshal in a building may tell us that in case of fire we should go down a few floors to one that is clear of the flame and smoke to wait there. Or we may be told to go all way the down and leave the building. Sometimes we’re given a choice. In any case, we have to take the stairs.

No system is perfect, or beyond question. Those choices may be beyond the physical means of some people, like those confined to wheelchairs or suffering from asthma, who may have to wait for assistance. And although it is rare, there have been times when there is no choice for anyone, and a total evacuation of a building is necessary. In some buildings, which can extend dozens of floors into the air, that means the staircases are going to be full for a long time.

That brings up another issue about evacuating occupants from high-rise buildings. Firefighters and other emergency personnel must get in to bring conditions under control. Often, they have to use the same stairs up that many others are using to get down. Sometimes, the responders have to stand and wait for their turn.

High-rise buildings for human occupancy—including some devoted to residences—are being built around the world. They are designed, of course, to contain fire and keep it from spreading throughout the structure. But that system can’t be perfect either, and so some fires may spread. And what about a building in which there has been an accidental explosion? Or an intentional one?

The attack on the World Trade Center in New York, and its loss of life, has prompted a rethinking of evacuation methods.

Two task groups of the ASME A17 Codes & Standards Committee on Elevators and Escalators are working now with issues involving the use of elevators during fires and other emergencies. Nothing has been decided yet, they say, and that reflects the complexity of potential hazards.

Designers, regulators, manufacturers, and riders are all familiar with elevators. They all know that elevators are off limits during fire alarms and drills, but many riders may not be sure why. Is it to keep the equipment in reserve for firefighters?

Mechanical Engineering magazine talked with the heads of the two A17 task groups. Edward Donoghue, code and safety consultant for National Elevator Industry Inc., leads a group that is considering the possibility of new code language governing the design and operation of elevators to help occupants evacuate buildings. David McColl, manager of codes and standards for Otis Elevator Co. in North America, heads a group investigating the possibility of hardening elevators for use by firefighters and other responders to emergencies.

According to Donoghue and McColl, conventional elevators can easily become deathtraps during a fire. Water delivered through sprinkler systems or sprayed from hoses to douse flames can run into hoistways, where it can short out machinery or cause brakes to fail. What’s more, whether an elevator is running or has lost power, a shaft filled with smoke can be a lethal environment.

In a paper, “Federal Investigation of the Evacuation of the World Trade Center on September 11, 2001,” delivered at the Pedestrian and Evacuation Dynamics Conference in Vienna in 2005, eight researchers from a variety of institutions—the U.S. National Institute of Standards and Technology, the University of Colorado, John Jay College, and National Research Council Canada—discussed the findings of their investigation into the occupant evacuation of the Twin Towers in New York.

Their recommendations, made on behalf of NIST, included consideration of “fire-protected and structurally hardened elevators” to assist in the evacuation of buildings and to bring responders to the site of an emergency. In their recommendations, the elevators would supplement ample stairway capacity.

The paper notes: “Elevators should be explicitly designed to provide protection against large, but conventional, building fires. Fire-protected elevators also should be structurally hardened to withstand the range of foreseeable building-specific or large-scale emergencies. While progress has been made in developing the requirements and technologies for fire-protected elevators, similar criteria and designs for structurally hardened elevators remain to be developed.”

The A17 task groups are working now to judge whether or not technology can, in fact, be developed to protect and harden elevators for safe use during emergencies. And if they decide the idea appears to be workable, the groups will recommend how to do it.

This past September, a NIST fire prevention engineer, Richard Bukowski, delivered an address to the International Interflam Conference in London in which he discussed ideas for emergency procedures in tall buildings.

Bukowski, who works at the agency’s Building and Fire Research Laboratory in Gaithersburg, Md., described a possible scenario for one day using elevators during a fire. “An elevator evacuation protocol is likely to begin with an initial alarm summoning the fire department and taking the designated fire service elevator out of service to await fire department arrival at the designated landing,” Bukowski said. “The remaining elevators will go into evacuation mode where they collect occupants of the fire zone (fire floor and two floors above and below) to shuttle them to the level of exit discharge.”

According to Bukowski, elevators are most efficient when they operate in a shuttle, or nonstop, mode because they avoid taking time to slow or accelerate smoothly. He suggested, too, that during an emergency, elevators should first move those people with the longest distance to go.

McColl and Donoghue said the elevator operation that Bukowski described is still some time off, if it ever comes. They said ASME’s review of the elevator codes for the purpose of emergency use began in 2004. Since then, the task groups have been wrestling with issues that arise from the idea. Each group has been conducting hazard analysis in its respective area. Each one has so far amassed more than 180 pages of hazard analysis documentation, and the work is unfinished.

Several organizations, including NIST, the National Fire Protection Association, the International Code Council, are participating in the task groups. So too are representatives of the elevator industry, firefighters, fire protection engineers, and many independent consultants, including experts on human factors, According to McCall and Donoghue, the majority of people participating in the task groups are not regular members of A17 committees.

The groups have considered a number of code changes. McColl pointed out that the nature of the changes means that they would almost certainly be applicable only to new construction. It would be prohibitively expensive to retrofit buildings to conform to the standard of a new fire-protected or hardened elevator.

According to Donoghue, the groups are first looking at fully sprinklered office buildings with full smoke detector systems for the evacuation system.

Since smoke is one of the hazards to contend with, there have been discussions about creating enclosed elevator lobbies that would also have direct access to stairways. Under this plan, as an additional protective measure, the lobbies and the hoistways they serve would be pressurized to keep smoke at bay.
Donoghue and McColl both said there is no consideration of allowing elevator service to continue for evacuation if a concentration of smoke is detected in an elevator lobby, hoistway, or machine room. Those elevators would be considered compromised and too hazardous for the public to use. They would return to the ground floor out of service until firefighters took over.

A building with more than one bank of elevators, remote from each other, might conceivably lose the service of one bank and have others remain available.

Ideas have been proposed to keep water from reaching hoistways, where it can flood pits and compromose critical safety circuits. One proposal, Donoghue said, is to build sloping floors that will drain water away from elevator lobbies. Strategic placement of small dams, scuppers, and drains might also keep water out of hoistways.

In his presentation in London, Bukowski talked about the importance of keeping everyone, especially occupants on the way out of danger, informed of changing conditions. “Real-time signs in every lobby would report system status in real time, including how long before cars would arrive to evacuate that floor,” he said. “The signs at the level of exit discharge would warn not to enter as the elevators are in evacuation mode. Conditions in the lobbies and machine room would be monitored in real time from the incident command. Once staging is completed, the fire service elevator can be used to pick up the injured or stragglers.”

The A17 task groups have not yet reached a consensus on how that can be done. According to Donoghue, the system would need a lot of signs and messaging to tell people what to do during an emergency. The human factors consultants are advising the task groups on those points, he said.

Once each task group deems its process of hazard analysis complete, it will decide on the next step. The hazards to human life may appear to be too great with available or even with anticipated technology. Or, the groups may propose changes in standards that may lead to revisions in code language.

According to McColl, it is possible that his group, which is studying the use of elevators by firefighters and other trained responders, may start writing proposals for the code in early 2008.

Donoghue said his group, which is studying occupant evacuation, is not as far along.

Both agree that no decision has been made. “Evacuation by elevators in a fire looks feasible,” Donoghue said. “It is premature to say it will go forward.”

home | features | breaking news | marketplace | departments | about ME
back issues | ASME | site search

© 2007 by The American Society of Mechanical Engineers