Issue 38: Applications of Elevators for Occupant Egress in Fires
By Richard W. Bukowski, P.E., FSFPE
For more than two decades, the elevator industry said that elevators
may not be safe to use for occupant egress during a fire. The Safety
Code for Elevators and Escalators (ASME A17.1)1 and the
building codes have required signs in every elevator lobby to advise
occupants to use the stairs and not elevators in case of fire. Their
main concern was that elevators may entrap occupants where they might be
exposed to smoke before the fire department can effect a rescue.
Following the World Trade Center attacks of September 11, 2001, it
became clear that evacuation of a very tall building can take too long
(evacuation of the WTC towers with the design occupant load was
estimated to require 4 hours).2 Such evacuations also involve
significant issues, including fatigue, people with pre-existing
disabilities or injuries received in the initiating event, and
unfamiliarity with the egress stair system.
Since 2004, the National Institute of Standards and Technology
(NIST), American Society of Mechanical Engineers (ASME), the elevator
industry, and other interested parties have been developing requirements
and procedures for occupant self-evacuation elevators that will be safe
to use in fires. The obvious benefits of using elevators for egress
include timely evacuation of very tall buildings, the provision of an
effective evacuation means for people with disabilities, and the ability
to provide for egress from assembly spaces high in buildings without
the need for increased stair capacity. These benefits are offset by the
cost in reduced rentable space of a building. However, egress elevators
have been installed in numerous tall buildings throughout the world
prior to the development of requirements and procedures.
During the development process, numerous technical papers were
presented at international conferences by participants discussing
approaches that were under discussion and were likely to be incorporated
into the final regulations.3,4,5,6 These papers became the
basis for many of the arrangements that were incorporated into buildings
as performance based design elements. Some existing buildings even
incorporated elevator evacuation protocols that were shown to reduce
total evacuation times. The result is many systems in use that do not
incorporate all of the features deemed necessary and which are
one-of-a-kind arrangements that may lead to confusion as the
standardized systems are put in place.
Stratosphere Tower7 (Las Vegas, NV)
Figure 1. Plan of the lower two floors of the pod showing the elevators and single egress stair within the shaft.
One of the many unique buildings gracing the Las Vegas skyline is
Stratosphere Tower, which is essentially an 11 story building (called
the pod) atop a slim base that is nearly 800 feet (240 m) tall.
The pod includes an observation deck, amusement rides, and a
restaurant; and it is accessed by four, double deck elevators that run
between ground level and the bottom two floors of the pod. These floors
are designated as areas of refuge (sized to accommodate the entire
occupant load in a noncombustible, sprinklered and pressurized space)
and contain additional elevators and escalators that provide access to
the other floors.
The base contains no occupied spaces, only the four elevator
hoistways and a single stairway (the base is so slim that a second
stairway would not be "remote"). From the outset, it was clear that the
elevators would need to be the secondary means of egress, if not the
primary. The project fire protection consultant began working with the
Las Vegas Fire Department to develop a performance-based design that
could be approved.
Because the elevators have only two stops (bottom and top) and there
is no fire exposure to the hoistway through the entire base, many of the
traditional concerns were not present. The double deck elevators were
to be under the control of trained operators at all times, so no
automatic protocol was needed. Two, separate machine rooms and a
fire-rated, dedicated shaft for emergency power provided needed
redundancy. One double-deck elevator would be used for fire department
access, leaving three for evacuation.
In consultation with the fire department, it was decided that the
performance criterion would be to evacuate the entire occupant load in
one hour by using the elevator. If one elevator was out of service for
maintenance or repair, the permitted occupant load (of 2600) would be
reduced by one third to maintain the one hour target. Entering and
exiting occupants are counted as they pass through turnstiles to control
the occupant load. The design was approved and the building is nearing
its 15th anniversary.
Petronas Towers (Kuala Lumpur, Malaysia)
Figure 2. Petronas Towers are connected by a skybridge at mid-height.
The Petronas Towers took the title as tallest building(s) in the
world in 1998. One tower is the corporate headquarters building for
Petronas Oil (the national oil company of Malaysia) and the other is
leased space. The two towers are connected at the 41st and 42nd floors
by a 58 m (190 ft) long skybridge. Built in accordance with a
combination of US and British codes, both towers have a reinforced
concrete core and contain firefighting shafts (with elevators) in
accordance with BS 5588 part 5.8
When first occupied, the emergency plan was based on the assumption
that the separation of the towers meant that no single event would
impact both. Thus, to reduce evacuation time, the plan was for occupants
of the affected tower below the skybridge to use the stairs to the
level of exit discharge, and occupants at or above the skybridge to use
the stairs to the skybridge, cross to the other tower, and use the
elevators to grade.
Shortly after the September 11, 2001 attacks in New York, there was a
bomb call to Petronas Towers that did not specify in which tower the
bomb was supposed to have been placed. The authorities decided to
evacuate both towers simultaneously, resulting in chaos. The bottom half
of both towers evacuated without problem, but the occupants above the
skybridge in Tower 1 tried to cross to Tower 2 as the occupants above
the skybridge in Tower 2 tried to cross to Tower 1. The skybridge jammed
and it took several hours to untangle the mess.9
In the aftermath, knowledge of the work getting underway in the US
caused the authorities to consider elevator evacuation. The new plan was
for the lower floors to evacuate by stair as before, but at or above
the skybridge occupants were to use the elevators in their tower to
grade. A drill to test the new plan resulted in total evacuation of both
towers simultaneously in just 20 minutes.
Taipei 101 (Taipei, Taiwan)
Taipei 101 took the tallest building designation from Petronas Towers
in 2004. Originally planned for traditional stair evacuation, a drill
conducted as the building neared completion resulted in an evacuation
time of about 2 hours. Aware of the activities underway in the US, the
Taipei Fire Department wondered if they could do better using the
elevators. They ran another drill incorporating the elevators and
observed an evacuation time of 57 minutes. This became the plan used
when the building opened.10
With both Petronas Towers and Taipei 101, the inclusion of evacuation
by elevator was made after construction so only limited modifications
could be made to enhance reliability; both buildings were constructed
with concrete cores and were fully sprinklered, so expansion of
emergency power to all egress elevators was considered sufficient.
One World Trade Center (New York, US)
Figure 3. One group of service cars provide fire access and egress in 1 WTC.
Designed by Skidmore, Owings and Merrill (SOM), the new One World
Trade Center is currently under construction on the former WTC site. The
building incorporates many design features in response to the NIST
recommendations from the WTC investigation, including some elevators for
occupant evacuation in fires, and a fire fighting shaft with elevator.
In the building, one group of (five) service cars is configured for
use in fires; one for fire service access and four for occupant
evacuation. As service cars, they are of larger capacity and stop at
every floor, but the number is only a fraction of the total, so most
occupants are expected to use the stairs. Until the building evacuation
plans are available, it is not clear who will have access to these
elevators (the disabled?) and how this will be controlled (fire
wardens?). The emergency generator supplying this group is located at
the top of the building so that the feeders do not need to be protected
for the entire height of the building.11
Applications in Asia
The building codes in China and several other Asian countries require
the provision of refuge floors every 15 or 20 floors in high rise
buildings. These floors (which usually share mechanical floors) provide a
space to rest, transfer between stairways, or to await assistance
during an evacuation. As egress elevators have been added to the system,
they frequently utilize shuttle cars (high speed and capacity cars that
travel only between the refuge floor and a skylobby) to move people
quickly to a safe place from which they can use stairs or another
elevator to reach the level of exit discharge. The impact on reducing
total egress time with and without these elevators has been estimated
for several buildings to be on the order of 25% (2 hrs 15 min for stairs
only versus 1 hr 45 min for stairs and elevators from the refuge
floors). A limitation for people with disabilities is that they still
need to use the stairs to reach a refuge floor from which they can
access the elevator.
In very tall buildings, zoned elevators are generally more efficient
in daily use; moving more people with less wait time and fewer
elevators. Also, current elevators are limited to a maximum lift height
of about 500 m (1640 ft) due primarily to the weight of the steel
cables. The development of new cable materials (polyimide ropes or PU
coated steel belts) should result in more height capability. Also, most
very tall buildings are mixed use, separated vertically. It is common to
provide separate elevator banks and lobbies for the different uses, so
some elevators travel through another use zone between grade and the
destination floors. This is often a section of blind shaft (no
openings) which is less exposed when passing a fire floor due to the
rated shaft wall, but presents issues of access for extraction of
entrapped passengers should an elevator stop in the blind shaft section.
Middle East Applications
Most tall buildings being designed and built in the Middle East are
being equipped with occupant evacuation elevators following similar
requirements to those under development in the US. Some designs utilize
refuge floors and some do not. In general, not all elevators are
arranged for evacuation use, and the design may assume about half the
occupants use elevators and half stairs. They typically provide
protected lobbies to wait for the elevator with direct access to an exit
stair should they decide not to wait. The emergency plans typically
follow phased evacuation and they assign (trained) building staff to
operate the elevators in an emergency to control the process.
The Burj Khalifa (Dubai UAE), now the tallest building in the world,
incorporates some elevators for occupant egress from each of the three
use areas (hotel, office, and residential). Comparison of total
evacuation time by stairs alone and by stairs (55% of 19,000 occupants)
and elevators estimated a 45% reduction in total evacuation time (to 90
min) with the elevators.
Safety Code for Elevators and Escalators, ASME A17.1-2007, American Society of Mechniccal Engineers, New York, NY.
Averill, J. et al., Federal Building and Fire Safety Investigation of
the World Trade Center Disaster; Occupant Behavior, Egress and Emergency
Communications, NIST NCSTAR 1-7, National Institute of Standards and
Technology, Gaithersburg, MD, 2005.
Bukowski, R.W., Emergency Egress from Ultra-Tall Buildings, Tall &
Green, Typology for a Sustainable Urban Future, CTBUH, Dubai UAE, March
Bukowski, R.W., Emergency Egress from Buildings, 7th International
Conference on Performance-based Codes and Fire Safety Design Methods,
Auckland, NZ, SFPE, 2008. and NIST TN1623, Nat Inst Stand Tech, 2009.
Bukowski, R.W., Emergency Egress Strategies for Buildings, Interflam
2007. (Interflam '07). International Interflam Conference, 11th
Proceedings. September 3-5, 2007, London, England, 159-168 pp, 2007.
Bukowski, R. W.; Fleming, R. P.; Tubbs, J.; Marrion, C.; Dirksen, J.;
Duke, C.; Prince, D.; Richardson, L. F.; Beste, D.; Stanlaske, D.,
Elevator Controls, NFPA Journal, Vol 100, No 2, 42-57, March/April 2006.
Quiter, J. R. Application of Performance Based Concepts at the
Stratosphere Tower, Las Vegas, Nevada. Rolf Jensen and Associates, Inc.,
Deerfield, IL. Fire Risk and Hazard Assessment Symposium. Research and
Practice: Bridging the Gap. Proceedings. National Fire Protection
Research Foundation. June 26-28, 1996, San Francisco, CA, 118-126 pp,
BSI 5588, Part 5, Fire Precautions in the Design, Construction and Use
of Buildings. Access and Facilities for Fire-fighting, British
Standards Institution, London, 2004.
Arliff, A., Review of Evacuation Procedures for the Petronas Twin
Towers, Strategies for Performance in the Aftermath of the World Trade
Center. CIB-CTBUH Conference on Tall Buildings. Proceedings. Task Group
on Tall Buildings: CIB TG50. CIB Publication No. 290. October 20-23,
2003, Kuala Lumpur, Malaysia, Shafii, F.; Bukowski, R.; Klemencic, R.,
Editors, 35-42 pp, 2003.
Hsiung, K.H., Wen, W.J., Chien, S.W., and Shih, B.J., A Research of
the Elevator Evacuation Performance for Taipei 101 Financial Center,
Proc 6th Int Conf on Performance-based Codes and Fire Safety Design
Methods, June 14-16, 2006, Tokyo, Japan, SFPE Bethesda, MD 213-225p,
Galioto, Carl, High Rise Evacuation and Life Safety, Skidmore, Owings
and Merrill (NY) presentation to AIA Annual Convention, Dallas, TX,
Richard Bukowski is with Rolf Jensen and Associates
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The Society of Fire Protection Engineers (SFPE) is a professional society for fire protection engineering established in 1950 and incorporated as an independent organization in 1971. It is the professional society representing those practicing the field of fire protection engineering. The Society has over 5,000 members and 100+ chapters, including many student chapters worldwide.