By Richard W. Bukowski, P.E., FSFPE
The National Institute of Standards and Technology (NIST) is leading a new effort to rethink the traditional stairwell-centered approach to emergency egress to embrace a more holistic strategy that includes all aspects of building design and operation, and their impacts on occupant safety. Clearly, elevators are a key component of this strategy. The effort began with a "Rethinking Egress" workshop in March 2008 and will continue in a series of workshops until a consensus of the engineering community is reached on how stairs, elevators, and other means of egress can meet the need for "timely" full evacuation of tall building occupants and response by emergency personnel.
One of the early conclusions from NIST's investigation of the events of September 11, 2001, was the need for "timely" full evacuation of tall building occupants and response by emergency personnel.1 At any significant height, stairs alone are clearly inadequate. In the late 1990s, NIST had worked with several Federal agencies and the elevator industry to study the use of elevators as a secondary means of egress (to stairs). This resulted in requirements in the Life Safety Code (NFPA 101) for elevators in air traffic control towers but an attempt to extend this to other occupancies in the model codes failed. A collection of papers from this effort were published.2 In 2003, NIST took the issue to the American Society of Mechanical Engineers (ASME) A17 Elevator and Escalator Committee, which develops and maintains the ASME A17 standards used throughout the US (and harmonized with the Canadian elevator standard
CSA B44). It was agreed to jointly organize a workshop to assess the feasibility of elevators that would be safe to use in the event of a fire in a building.
This workshop was held in March 2004, and there was a consensus among the fire service and elevator industry that it was feasible with current technology to make elevators safe for use by both occupants and the fire service in a building with a fire condition. The key observation leading to this consensus was that the requirements implemented in the 1980s in the
ASME A17.1 standard was effective in sensing the onset of hazardous conditions and taking elevators out of service ahead of unsafe conditions.
In the 1970s, there was a small number of incidents where occupants, firefighters or the fire itself, called an occupied elevator to the fire floor and opened the door onto untenable conditions (e.g., First Interstate Bank fire3). Light beams that prevent the landing doors from hitting passengers when they close were blocked by smoke, holding the doors open and preventing the car from leaving. The response from the elevator industry was twofold. First, firefighters' emergency operation (FEO) was developed and mandated on all new and upgraded elevators. FEO involves smoke detectors located in every elevator lobby and machine room that, when activated, take all elevators out of service, returning them to the designated level (of exit discharge) opening the doors, and locking them out of service. This is called Phase I recall. If the fire is on the designated level, the elevators are sent to an alternate level. The second industry response was to require signs in every elevator lobby warning not to use the elevators in fires, but to use the stairs.
The elevators are intended to be placed into Phase I recall on activation of an elevator lobby or machine room smoke detector and not for any other alarm in the building. Thus, the elevators will continue to operate in what is called normal service with a fire in the building unless Phase I is activated. Fire departments have a manual means to activate Phase I, which some utilize in order to take control of the elevators and prevent occupants from unknowingly traveling to the fire floor or becoming entrapped. Once on Phase I, firefighters can place individual cars into a manual operation mode called Phase II with a firefighter's key in a keyswitch located in the car. Phase II operation does not respond to hall calls and utilizes a special operating mode for the car controls that reduces the risk of the firefighter being exposed to fire conditions, including disabling the door light beams (see ASME A17.4).4
Based on the 2004 workshop consensus that elevators could continue to be used safely with a fire in the building until Phase I was initiated, ASME organized two task groups (one on use of elevators by firefighters and the other on use of elevators for occupant egress) to carefully study any hazards that might result and the means to mitigate these hazards. These task group activities are nearing completion, and a second workshop to share the results of the task group deliberations (including a several-hundred page hazard analysis) is planned for October 2009.
In the mid-1980s, the British adopted a requirement for a firefighter elevator as part of a firefighting shaft in all new high-rise buildings (>30 m). They developed and published a standard5 which has recently been converted (with little change) to a European standard.6 These firefighter elevators are now common in tall buildings in England and other countries that traditionally follow British Standards. Not surprisingly, the ASME work is leading to recommendations that are very similar to the British/European standard.
Due to the high level of training and preplanning common to fire department operations (and especially high rise firefighting operations) the fire service should be familiar with the system and its safe operation (ASME publishes ASME A17.43, as a training guide on elevator emergency operating procedures for the fire service). This is not true for occupant use elevators, so the occupant egress elevator is a more complex issue to the extent that their use differs from the occupants' everyday use of the system.
Current thinking (not yet finalized by the ASME task group) is that on any fire alarm in the building, the firefighter elevator(s) will be placed in Phase I to await the arrival of the fire department at the level of fire department access. The remaining elevators will evacuate the occupants from the fire floor, two floors above and two below, to the level of exit discharge and then be taken out of service to control occupant movement while the situation is assessed by the fire department. Such a phased (or partial) evacuation procedure is commonly followed in high rise buildings using the emergency voice evacuation system to direct occupants on the five floors to the stairs and (in some cases) informing occupants in the rest of the building to await further instructions.
Should the incident commander decide that full building evacuation is necessary, the elevators would be placed into full evacuation mode, unloading the building from the top down. The system would follow this top down priority, ignoring hall calls, except that these would register that occupants are awaiting elevators on those floors. If these floors had already been evacuated, cars could be sent back or fire service cars operating on Phase II used to collect occupants.
Each floor would have a fire and smoke rated elevator lobby to provide a protected waiting space and that provides a barrier from the fire. This would delay automatic activation of
Phase I, which would terminate elevator evacuation. Informational displays in the lobbies would assure occupants that the elevators are in service evacuating people, and a direct access to an egress stair from the lobby would provide an egress path if the elevator evacuation is halted. A pressurized hoistway would protect the elevator and lobby from smoke, and provisions to protect the elevator components from water are included. Emergency power, protection of the power and control wiring, and protection against water intrusion rounds out the protection package.
While both firefighter and occupant elevators have additional costs for safety features, the costs are low compared to the cost of wider or more egress stairs. It is interesting to note that the elevator industry design practice for normal use (to meet the demands of the start and close of the business day) results in a number, capacity, and speed to permit the self evacuation of 100% of the building population in 30 minutes to one hour (based on an industry standard design handling capacity of 12.5%7).
The benefits of using elevators are so obvious that the building codes are changing rapidly and most tall buildings are being outfitted with elevators for egress and access even before the codes and standards can be changed. In their 2009 editions, the International Building Code8 (IBC), NFPA 1019 and NFPA 500010 require fire service elevators in all new buildings over
120 feet (37 m). The City of San Francisco adopted (effective in January of 2008) a change to their building code requiring fire service elevators in new buildings exceeding 200 feet11 (61 m). Fire service elevators are included in the designs of Freedom Tower (NYC), Burj Dubai (UAE), Chicago Spire (Chicago) and many others.
NFPA 101 and NFPA 5000 incorporate an adoptable annex containing requirements for occupant evacuation elevators but do not require their use in any occupancy or any threshold building height. The IBC 2009 contains similar requirements in the body, but also no requirement by occupancy or height threshold. This approach was considered more appropriate for such a significant code change. Occupant elevators are also incorporated in Freedom Tower, Burj Dubai, Chicago Spire, One Financial Center Shanghai (a modified approach where the express elevators normally serving the observation deck will stop at the required refuge floors in a fire) and others.
Richard Bukowski is with the National Institute of Standards and Technology.
- Final Report of the National Construction Safety Team on the Collapses of the World Trade Center Towers. NIST NCSTAR 1. National Institute of Standards and Technology, 2005.
- Bukowski, R.W., Burgess, R. and Reneke, P., Collected Publications Related to the Use of Elevators During Fires, NIST SP 983, May 2002, http://wtc.nist.gov/pubs/elevators/
- Morris, J., First Interstate Bank Fire – What Went Wrong? Fire Prevention, No. 226,
20-26, Jan/Feb 1990. - Guide for Emergency Personnel, ASME A17.4-1999, ASME New York.
- BSI 5588, Part 8. "Fire precautions in the design, construction and use of buildings. Code of practice for means of escape for disabled people," British Standards Institution, London, 1999.
- EN 81-72, "Safety rules for the construction and installation of lifts - Particular applications for passenger and goods passenger lifts - Part 72: Firefighters," European Committee for Standardization (CEN), Brussels.
- Strakosch, G.R., The Vertical Transportation Handbook Third Edition, John Wiley & Sons, Inc., New York, 1998.
- International Building Code, International Code Council, Falls Church, VA, 2009.
- NFPA 101, Life Safety Code, National Fire Protection Association, Quincy, MA, 2009.
- NFPA 5000, Building Construction and Safety Code, National Fire Protection Association, Quincy, MA, 2009.
- San Francisco Fire Code, Section 5.08, Jan 2008.
