New Evacuation Procedures Proposed: Evacuation 911
January 01, 2006
Appeared in Building Operating Management/FacilitiesNet
After more than four years, it’s possible to forget not only how tragic the events of Sept. 11, 2001, actually were, but also how much more tragic they could have been. Had the buildings been fully occupied, the National Institute of Standards and Technology (NIST) has estimated that it would have taken more than three hours to fully evacuate the buildings. In the process, 14,000 people — 28 percent of the occupants — would have died because of insufficient stairwell capacity.
Those stark numbers prompted NIST to call for changes in high-rise building design to improve evacuation time in an emergency. If the recommendations are adopted, facility executives could one day oversee high-rise buildings that have timely full building evacuation plans for non-fire emergencies. The buildings would have hardened elevators and stairwells. Stairwells would be wider and spaced farther apart, and upgraded elevators would be used for evacuation and for emergency responders.
But the NIST recommendations are both controversial and broadly defined, which means industry code bodies will have a significant role to play shaping the recommendations into code — if they are adopted at all.
New Approach to Evacuation
High-rises have been built assuming that the entire building wouldn’t need to be evacuated at once. Instead, during a fire on one floor, occupants evacuate to adjacent floors until it is safe to return.
What does timely full building evacuation entail? NIST’s recommendation says that a building’s size, population, function and iconic status should be taken into account in designing an egress system. “The key question is how much time should be allowed or specified for total safe evacuation,” says Milosh Puchovsky, principal fire protection engineer for the National Fire Protection Association (NFPA).
There is little agreement about how much time should be allowed for a full building evacuation because the topic is relatively new, says Ron Klemencic, chairman of the Council on Tall Buildings and Urban Habitat. “Clearly, if you put in 10 stairwells, you could get people out of the building much faster,” he says. “But how fast is fast enough?”
A full building evacuation during a prolonged power outage, for example, would not necessarily need to be rapid. An explosion, however, might require faster evacuation.
Even if there is disagreement regarding how fast a full building evacuation should be, elevators, stairwells and evacuation plans will all need major revisions to make full evacuation practical.
Structural Changes Required
The final NIST report on the collapse of the World Trade Center towers indicated that the overall evacuation rate in WTC 2 was 108 survivors per minute, about 50 percent faster than WTC 1 at 73 survivors per minute. That’s because occupants in WTC 2 used the elevators in the 16 minutes before the second tower was struck.
For more than 30 years, building occupants have been told not to use an elevator during a fire. With new recommendations from NIST for full building evacuation, the American Society of Mechanical Engineers (ASME) is examining whether elevators could safely be used to evacuate high-rises during an emergency.
Designing elevators that could safely be used during a fire or other emergency is a serious challenge, says Edward Donoghue, administrator for the National Elevator Industry Inc. (NEII) and a safety and codes consultant. For example, one hazard that needs to be overcome is keeping water used during firefighting out of the hoistway, Donoghue says. ASME is conducting separate hazard analyses to see whether elevators can safely be used by occupants for evacuation and whether they can also be used for emergency responders during a fire or other emergency. The NIST report also recommends emergency responders have access to a dedicated elevator.
“It’s a very extensive analysis,” Donoghue says. “It’s probably going to take another couple of years to complete.”
Upsides and Downsides
While elevators factor into the timely evacuation of high-rise buildings, NIST has not ignored stairwells. NIST recommends designing stairwells wide enough to accommodate both descending occupants and ascending emergency responders. That means wider stairwells. “For certain size buildings, provisions have already been implemented in NFPA 101 and NFPA 5000 that require additional stair width to accommodate the counterflow of emergency responders,” says Puchovsky. NFPA 101 is a life safety code. NFPA 5000 is a model building code.
The 28-story Cira Centre in Philadelphia, for example, has stairwells that are 50 inches wide, as opposed to the 44 inches required by code. Construction on the building began in 2003, and the stairwells were voluntarily widened, says Stephen Rush, leasing agent for Brandywine Realty Trust.
NIST has also recommended that stairwells be marked with consistent signage, be located farther apart without increasing average travel distance and maintain their integrity under foreseeable building-specific or large-scale emergencies. Each World Trade Center tower had three emergency stairwells, but only one stairwell in WTC 2 remained passable after the towers were struck, according to NIST. Increasing stairwell distance means more stairwells could move from the building core to the perimeter.
However, maximizing the distance between stairwells could slow evacuation as it takes longer for occupants to reach a stairwell, Klemencic says.
New York City’s World Trade Center Building Code Task Force issued a variety of recommendations in 2003 that are now required by the city’s Local Law 26. Three requirements regarding stairwells apply to buildings 75 feet and higher and are retroactive. Photoluminescent markings are required in all exit doors and exit stairs. Additional signage is required when the exit path is not clear and such signs must have battery or generator power.
Disaster planning in a post-9/11 world means evacuation plans should move beyond fires. Power outages, earthquakes, tornadoes, fires, explosions and terrorist attacks should all be taken into account when evacuation plans are formulated, according to NIST.
“When we are talking about full building evacuation, we are talking about evacuation for potentially any type of situation,” says Jim Carrigan, supervising engineer for fire and life safety for the Syska Hennessy Group. Prior to 9/11, for example, facility executives really didn’t talk about hazardous material issues when formulating evacuation plans.
Unlike NIST’s recommendation for full building evacuation, the recommendation for better evacuation planning appears to be gaining traction.
In one case, a tenant occupying multiple floors in a high-rise paid to have its evacuation plan reviewed and upgraded after the developer declined, says Carrigan. The original plan only contained provisions for a fire emergency, while the revised evacuation plan was broadened to take other potential emergencies into account. It was later adopted by all 40 building tenants, Carrigan says.
In New York City, Local Law 26 requires that emergency evacuation plans include non-fire-related events. “The idea was that while the codes have had sufficient fire protection and fire safety plans, the conditions of other emergencies that are not directly related to a fire have not been considered,” says Ronny Livian, chairman of the World Trade Center Building Code Task Force.
In earthquake-prone Seattle, a full building evacuation plan doesn’t necessarily make sense, says Ben Barron, vice president of development for Clise Properties, which manages 1700 Seventh Avenue, a 23-story office building. “We feel that the tenants are safer in our building than out on the street, at least until we analyze what is going on.”
Barron says that a man threatened to blow himself up while standing in the lobby of a nearby courthouse. Rather than completely evacuate the 1700 Building, tenants were moved away from the side of the building nearest the courthouse. The reason? Tenants who left the building likely would have gathered in a courtyard near the courthouse, placing them in danger.
Beyond the Exits
Facility executives can’t forget about occupants once they leave a building. Proper planning means making sure occupants remain safe once they are evacuated, says Livian.
“In a larger building, you may have an occupant load of 10,000 or 20,000,” he says. “Where do you put them and still be safe? You can’t just leave them out in the street.”
To be successful, full building evacuation plans must be tailored for specific buildings and the types of occupants in the buildings, says Carrigan. In addition, the plans require training so that facility executives know when it is appropriate to call for a full evacuation and when to call for a phased evacuation. What’s more, facility executives should not call for a full-building evacuation by paging the entire building and asking occupants to leave, as was the case on 9/11, Carrigan says.
“The purpose of a full building evacuation is to do a staged evacuation in a controlled manner,” he says. “With the current buildings, if the stairwells haven’t been widened, you have to do a staged evacuation or there will be a bottleneck.”
Comprehensive disaster planning also means accounting for mobility-impaired occupants. According to NIST, 6 percent of the occupants in the World Trade Center were mobility-impaired. In a traditional phased evacuation, mobility-impaired occupants can be moved away from a fire or other emergency with relatively little difficulty. A full building evacuation is more troublesome. Knowing which occupants are impaired and where they are located is key. Ideally, an evacuation plan also takes into account visitors and occupants who are temporarily impaired because of illness. In the case of non-fire emergencies, Carrigan recommends using elevators to evacuate mobility-impaired occupants.
In Seattle, Clise Properties has identified mobility-impaired tenants. In case of an emergency, a “buddy system” has been arranged to make sure the mobility-impaired tenants can get the assistance needed to evacuate, if necessary. The company has ordered an evacuation chair that will allow occupants to be evacuated down a stairwell, Barron says.
Even if the NIST recommendations governing full building evacuation and elevators are approved by code bodies, implementation will likely take years. While not all cities require high-rises to develop separate emergency action plans for fire and non-fire events, a proper plan that considers fire and non-fire-related emergencies can ensure that a building disaster doesn’t become a greater tragedy.
“In a post-9/11 world, everybody needs to have an emergency evacuation plan for fire and non-fire events,” says Carrigan. “We have different threats today.”