Down from the Stratosphere
From the Las Vegas Strip, a lesson in elevator-based evacuation.
NFPA Journal®, July/August 2009
By Lisa Nadile
A stunning 921 feet (281 meters) up in the air, a high-speed, spider-like ride twirls passengers at 40 miles (64 kilometers) per hour around the twelfth story of Stratosphere Tower’s 13-story occupancy pod. On the 13th floor sits another thrill ride that shoots passengers up about 160 feet (49 meters) and fires them back down. The pod to which the rides are attached is itself attached to four legs and a concrete core, and looks not unlike the Martian ships H.G. Wells describes in "The War of the Worlds."
It should come as no surprise that this wacky building is located in Las Vegas, Nevada, or that the tenant pod contains a wedding chapel, as well as a revolving restaurant, two observation decks, and two areas of refuge near the building’s four elevators on two of the pod’s floors. This design, like that of many of the structures in Las Vegas, was performance-based and rethought a number of commonly held beliefs about elevator evacuation. When the Stratosphere Tower opened its doors, and its elevators, to the public in 1996, it brought with it an emergency management plan that made elevator evacuation a critical component.
Long discussed, the concept of using elevators to evacuate high-rise buildings was thought potentially dangerous until 9/11, when the feasibility of elevator evacuation in special cases drew new attention, particularly given technological advances in mass notification and elevator equipment. Elevators are optimum in high-rise evacuations, especially for the less physically able, says City of Las Vegas Fire Protection Engineer Azarang Mirkhah, P.E., who helped develop the fire and life safety protection plan for the Stratophere Hotel, Casino, and Tower Complex.
In case of a fire in the Stratosphere Tower pod, occupants would first use the stairs to go to the two areas of the refuge at the bottom of the pod. There, the elevator operators would evacuate the occupants to the base of the tower. "It is important to recognize that the elevators evacuating the areas of refuge at the bottom of the pod to the base of the tower will not be traveling through any areas compromised by fire, and the doors would only open and discharge at the bottom," Mirkhah says. The evacuation would be complete within an hour.
"Naturally, they can use the stairs if they’d prefer," he says.
In fact, most people are generally inclined to use the stairs, having been told for decades to avoid elevators during a fire. The message to avoid elevators is so ingrained in public consciousness that changing it will be a monumental task, says Mirkhah, particularly as occupants must initiate elevator evacuation themselves.
"Real-time signage with messages will be required at the elevator landing [on each floor] to inform the occupants about the emergency conditions, so they are expected to press the button for the lobby or exit," says Ron Coté, NFPA’s principal life safety engineer and staff liaison to the Life Safety Code technical committees.
The 2009 edition of NFPA 101®, Life Safety Code®, contains Annex B, Elevators for Occupant-Controlled Evacuation Prior to Phase I Emergency Recall Operations, which states that, "with respect to existing technology and products, the elevator will continue to run under its normal programming mode until the elevator is called out of service by detection of smoke at an elevator landing or in the elevator machine room," says Coté. This means that as long as an elevator has not been recalled to the lobby during an emergency, anyone on any floor can use it to travel to any other floor. However, the Stratosphere Tower elevators sense the weight they carry, and if the weight limit has been reached, the elevator will travel directly to the lobby, bypassing any remaining floors.
At the Tower, turnstiles are used to track the occupancy of the building so that the population does not exceed the number that the three elevators could evacuate in one hour. "The responders will probably be using the fourth elevator," Mirkhah says.
"But what I’m concerned about in normal buildings that are contemplating elevator evacuation is the elimination of redundant and balanced passive and active fire protection in favor of just sprinklers," he says. "I don’t think in the existing old high-rise buildings that do not have the degree of fire protection redundancies that we should change the message to the building occupants and tell them that it is proper to use the elevators. No, they should still use the stairs. That would be confusing and contradictory, which could be dangerous," Mirkhah says. "When they build new modern high-rises with better codes and a higher degree of fire protection, then it is alright to use the elevators."
The Stratosphere Tower has just such a degree of fire protection. There are no combustibles near or in its reinforced concrete elevator shafts. Its passive fire protection, such as the use of concrete and masonry, smoke control, and fire-rated interior construction, reinforces the fire sprinkler system.
"I also think in many cases even the fire service professions do not utilize all their fire protection resources [during a response to an incident]," says Mirkhah. This means the fire service will also have to train and re-conceptualize their response for high-rise elevator evacuation, he says.
New technology for automating elevators will make organizing their use during an emergency easier, says Coté. With respect to the new technology we can expect, he envisions that a group of floors will be given priority service, depending where the alarm-initiating signal originated. The "designated floors" might include the fire floor, two floors immediately above it, and one floor immediately below. Elevators will be dispatched to the designated floors, and no "calls for elevator" will be accepted from any floors other than the designated floors. The occupants, who will have been instructed to proceed to certain floors or areas of refuge, will enter the elevator cars, which will be dispatched "express" to the level of exit discharge, typically the ground floor lobby. Once empty, the elevator car will return to the designated floors until there are no additional occupants to transport. Elevators will then be dispatched to the highest levels outside of the designated floors. Dispatching will work its way down through the building. People will be directed, especially in high-rise buildings, to certain floors or areas of refuge. Elevators will dispatch to those floors for evacuation.
By the time this scenario becomes fact, the Life Safety Code committee hopes the public will have learned to consider using elevators during an evacuation. "A more refined occupant evacuation elevator is expected for the future editions, and it will use new technology and standards," says Coté.
Using elevators in a high-rise evacuation in buildings with proper fire protection is just common sense, Mirkhah says, and occupants should be instructed in the use of both stairs and elevators in those buildings.
Lisa Nadile is associate editor of NFPA Journal.