Using elevators in fires

07/21/2010


Engineers in the United States are rethinking the traditional stairwell centered approach to emergency egress from buildings and embracing a more holistic strategy that includes all aspects of building design and operation, and their impacts on occupant safety.

Elevators are a key component of this strategy. The effort is targeted at developing a consensus of the engineering and regulatory communities on how stairs, elevators, and other means of egress can meet the need for “timely” egress from and access to tall buildings in emergencies including fires.

An early conclusion of the National Institute of Standards and Technology (NIST) investigation of the Sept. 11, 2001, events was the need for “timely” full evacuation of tall building occupants. Additionally, uninhibited access by emergency personnel is required. Above about 40 floors, egress can take more than 1 hour, so stairs alone are clearly inadequate. In the late 1990s, NIST 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 changes in the Life Safety Code (NFPA 101) that allowed the use of elevators as a secondary means of egress in air traffic control towers, but an attempt to extend this to other occupancies in NFPA 101 never came about.

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 United States (and harmonized with the Canadian elevator standard CSA B44). They jointly organized a workshop to assess the feasibility of elevators that would be safe to use during a fire in a building.

At the March 2004 workshop, fire service and elevator industry participants came to a consensus 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. The key observation leading to this consensus was that the hardware arrangement and procedures of Firefighters Emergency Operation (FEO) 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 were a small number of incidents where occupants, firefighters, or the fire itself (heat-sensitive hall call buttons) called an occupied elevator to the fire floor and opened the door onto untenable conditions (for example, the First Interstate Bank fire). Light beams that prevented the landing doors from hitting passengers when they closed were blocked by smoke, holding the doors open and preventing the car from leaving.

Occupied elevators
The response from the elevator industry was twofold. First, FEO was developed and mandated on all new and upgraded elevators. FEO requires smoke detectors to be located in every elevator lobby and machine room so that when activated, all elevators are taken out of normal service, returning them to the designated level (of exit discharge), and opening the doors. 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.

The elevators are intended to be placed into Phase I recall on activation of a smoke detector located in any elevator lobby or machine room and not for any other alarm in the building. Thus, the elevators will continue to operate in 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 use 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 key switch located in each car. Phase II operation does not respond to hall calls and uses a special operating mode for the car controls (Table 1) that reduces the risk of the firefighter being exposed to fire conditions, including disabling any door light beams intended to prevent doors from hitting passengers (see ASME A17.4).

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 December 2010.

Outside the United StatesIn the mid-1980s, England and Wales adopted a requirement for a firefighter elevator as part of a firefighting shaft in all new buildings taller than 30 meters. They developed and published a standard (BS 5588 part 5), which has recently been converted (with little change) to a European standard (en81-72). 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.

 

Other parts of the world, such as China, also require any building taller than 24 meters (defined as high-rise buildings) to have a minimum number of firefighter elevators based on the floor area (buildings less than 1,500 sq meters are required to have one fire fighter elevator; those 1,500 to 4,500 sq meters, two firefighter elevators; and those more than 4,500 sq meters, three firefighter elevators). However, no Phase II elevator operation is included in the China code, and it recalls the elevators to the designated or alternate level (like Phase I) on any fire alarm in the building.

Fire departments, especially those responsible for interior attack of fires in high-rise buildings, are expected to provide training on the safe use of these fire service elevators. ASME A17.4, which is used as a training guide on elevator emergency operating procedures for the fire service, will be updated with information on the new systems. The situation is quite different for occupant use elevators, especially in buildings with high transient populations; the occupant egress elevator is a more complex issue to the extent that the emergency use differs from the occupants’ everyday use of the system. Cultural differences also need to be taken into account with respect to behavior under emergency conditions.

Current thinking is that on any fire alarm in the building, the firefighter elevators will be recalled 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—plus two floors above and two below—to the level of exit discharge. A floor is considered clear when no more hall calls are registered. Then the elevators will be taken out of service to control occupant movement within the building 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 fire 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 manually placed into full evacuation mode, unloading the building from the top down. The system would follow this top-down priority, ignoring any hall calls except that these would register that occupants are awaiting elevators on those floors. If these floors already had been evacuated, cars could be sent back or fire service cars operating on Phase II used to collect occupants. This would continue until the building is emptied of occupants.

Each floor would have a fire- and smoke rated elevator lobby to provide a protected waiting space and to provide a barrier between the fire and the elevator. This barrier would delay automatic activation of Phase I, which would terminate elevator evacuation. In a fully sprinklered building, smoke entering the lobby while occupants are entering would not contaminate the lobby. Informational displays in the lobbies (including an estimate of the time in minutes before the elevators serve that floor) assure occupants that the elevators are in service evacuating people, and direct access to an egress stair from the lobby provides a safe egress path if the elevator evacuation is halted. 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 these safety features, the costs are low compared to the cost of wider or more egress stairs, and elevators move people far more efficiently using the envisioned emergency evacuation operation protocol. 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 of elevators to permit the self-evacuation of 100% of the building population in 30 to 60 min (based on an industry standard design handling capacity of 12.5%). With current elevator technology, speeds up to 10 meters/ sec are achievable, and double-deck elevators found in some very tall buildings can move more people with fewer hoistways.

Codes and standards
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 Code (ICC) and NFPA 101/5000 require fire service elevators in all new buildings taller than 120 ft. The City of San Francisco adopted (effective in October 2008) a change to its building code requiring fire service elevators in new buildings exceeding 200 ft. Fire service elevators are included in the designs of Freedom Tower (United Arab Emirates), Chicago Spire (Chicago), and many others.

The NFPA 101/5000 2009 edition incorporates an adoptable annex containing requirements for occupant evacuation elevators, but does not require their use in any occupancy or any threshold building height. Similarly, the IBC 2009 contains requirements in the body, but also no requirement by occupancy or height threshold. In both cases, there is no credit against required egress capacity for occupant elevators. The IBC exempts its new requirement for a third stair in buildings taller than 420 ft where occupant elevators are provided. (This requirement is not found in NFPA 101/5000.) Occupant elevators are also incorporated in Freedom Tower, Burj Khalifa, Chicago Spire, One Financial Center Shanghai (China; a modified approach where the express elevators normally serving the observation deck stop at the required refuge floors in a fire), and others.

Egress elevators have been used in several tall buildings to avoid increases in egress stair capacity required where the buildings incorporate assembly uses at the top—observation decks, restaurants, and lounges. Examples where these have been successfully employed include Stratosphere  Tower (Las Vegas), Swiss Re Building (London), and One Financial Center (Shanghai, China). Several countries have expressed significant interest in adopting egress elevators as part of their disability regulations. Examples include the United States, Canada, Australia, New Zealand, and Japan. In the United States, the United States Access Board is considering a finding that occupant egress elevators that are in accordance with the IBC or NFPA requirements will be considered to satisfy the requirement for an Accessible Means of Egress, which currently requires at least one elevator in buildings with an accessible floor above the third floor.

The global interest in fire safe elevators is one of several examples of common objectives and approaches to fire and life safety provisions for tall buildings. In many Asian countries, including China, that have numerous current and future developments of super high-rises, the existing requirement for refuge floors in buildings with heights higher than 100 meters can benefit from the provision of elevator egress. The use of refuge floors is an accepted practice in these countries, Petronas Towers in Kuala Lumpur, Malaysia, reduced their total evacuation time from 2 hr to 20 min by incorporating elevators for occupants above the skybridge level. Photo: Richard Bukowski but not common in the United States. Elevators with these enhanced protection levels include a safe space for people to await being evacuated via elevator, and provide sufficient information to prevent apprehension common in emergency conditions.

About the authors
Bukowski is a senior consultant. Li is an executive vice president.



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