Features

NFPA Journal®, November/December 2003

• Unconventional exit strategies
• Chute- and slide-based devices
• Rescue systems
• Parachute systems
• Regulatory and listing issues
• Human factors

Since the collapse of the World Trade Center on September 11, 2001, the fire safety community has received numerous suggestions concerning emergency evacuation techniques for high-rise buildings, ranging from widening existing exit stairways to using specialized equipment to help occupants escape in an unorthodox manner. In general, the proposed evacuation methods can be classified as either traditional, meaning they were used in high-rise applications before 9/11, or unconventional, meaning that they are relatively new or untried concepts, or concepts that, until now, have been prohibited in the United States.

While not recognized by NFPA 101®, Life Safety Code®, or NFPA 5000™, Building Construction and Safety Code™, some of these methods are used voluntarily at building sites in the United States and by mandate in other countries. And articles on these devices have even appeared in the mainstream media, from The Wall Street Journal to Popular Science. The purpose of this article is to provide some basic information on these alternative egress devices with which we, as building safety professionals, should be familiar—even if we don't condone their use.

Unconventional exit strategies
Conventional approaches to high-rise fire safety planning currently integrate active and passive construction features, such as compartmentation, fire sprinklers, and pressurized stairwells, that have proven reliable over the years. Unconventional exiting approaches, on the other hand, may include such nontraditional safety measures as winch-like lowering systems, escape chutes, and parachutes designed to dissipate the kinetic energy developed by descending evacuees to deposit them safely on the ground at a manageable speed. (Note 1) Such devices pose significant technical challenges and questions about potential regulatory issues and human behavior.

Currently, unconventional exiting strategies aren't typically part of U.S. system design, emergency planning, or regulatory review, although NFPA 101 and NFPA 5000 do address evacuation slides to a limited extent since they're used by industrial facilities, such as oil-cracking towers, and in air traffic control towers on some military bases. Despite our lack of familiarity with, or use of, such systems in the United States, however, many are used in other countries. (Note 2)

Winch-like systems lower evacuees from tall buildings using a cable and a braking mechanism to control the speed of descent. The lowering device most widely used today is the Japanese-made ORIRO Descenter, composed of a pulley and a steel rescue cable with woven-cotton harnesses at both ends. To use the system, an evacuee attaches the pulley to a window, roof, or balcony mounting bracket and dons the harness, in which he or she is lowered to the ground at a speed of 3 feet (1 meter) per second. As the evacuee descends, the harness at the other end of the cable rises up to the spot he or she left, allowing the next evacuee to use it. The pulley controls the descent rate using a centrifugal friction brake.

More than 100,000 UL-listed Descenters, which can hold individuals weighing up to 225 pounds (102 kilograms), are reportedly in use in Japan.

The BEST Rescue System, which is manufactured in the United States, is similar in concept to the Descenter, but it employs two fire-resistant suits instead of cotton harnesses to hold evacuees. The suits, which resemble large overalls that extend over the evacuee's head, are designed to reduce heat exposure and ease anxiety by preventing a view of the ground below. They are attached to a cable and a pulley that pulls an empty suit up for the next person to use as the evacuee descends.

A former commissioner of the New York City Police and Fire Departments, Howard Safir, is marketing the newest lowering approach, the Safir-Rosetti ResQline. This system provides a faster rate of descent using the air resistance created by a spinning turbine that dissipates the kinetic energy generated during lowering. The ResQline, which measures 3 by 3 by 1.5 feet (1 by 1 by 0.5 meters), can be installed in one or two locations per floor and on rooftops, balconies, or in any window that opens.

In case of a fire, an evacuee puts on a harness attached to a portable spool of cable. After attaching the spool to the axle of the turbine, the evacuee steps away from the building and descends at about 15 feet (5 meters) per second as the turbine controls the descent. After the evacuee lands, the next person removes the previous user's spool, and the procedure is repeated. The UL-listed system, which allows evacuees to descend roughly five times faster than the centrifugal friction brake systems of the Descenter and the BEST Rescue System, can be used for buildings of any height and is reported to be maintenance-free for indoor and outdoor use for up to 35 years.

Recently, the Azrieli Center in Israel— a mall and business towers in the center of Tel Aviv—purchased the Safir-Rosetti ResQline system.

Chute- and slide-based devices
Chute- and slide-based devices typically use a fabric tube deployed from a location up to 30 stories above the ground and require run-out room to allow evacuees to slow before exiting.

The Baker Life Chute (BLC), one of which is installed at the Ramstein Air Force Base air-traffic control tower in Germany, is a nylon netting tube attached to three metal rings at the top and bottom. The upper rings are secured to the structure from which the evacuation is taking place, and the lower rings are secured to a fixed, pre-determined object on the ground. Evacuees slide down the tube and slow themselves by applying outward pressure on the net with their feet and hands. The system, manufactured by Baker Safety Equipment of Delaware, can reportedly carry as many as 30 people at a time in a continuous flow.

Another BLC system is designed to be airlifted to the top of a building during an emergency, while a third can be attached to the bucket of a fire department rescue ladder.

In the Advanced Modular Evacuation System made by an Israeli company, an enclosed chute of fire-resistant material is automatically deployed from a portal inside the building to a designated location on the ground or on an adjacent building when the building's fire alarm system activates. Flat sections in the tube control descent speed. After the occupants have evacuated, rescue personnel can use a winch system built into the chute hardware to enter the building.

Rescue systems
Then there's the Escape Rescue System, manufactured by Escape Rescue Systems Ltd. of Kadima, Israel. It's stored folded on the roof; when deployed, multi-platform arrays are opened and lowered to sets of floors, enabling occupants to enter simultaneously through marked windows. The arrays are lowered to the ground, and tenants exit to safety as the arrays refold. Fire and rescue personnel ride the system up and into the building.

Parachute systems
Another unconventional evacuation device is the parachute, derived from classical parachutes, which requires evacuees who jump from a structure to exercise some control as the descent occurs. Professional parachutists, including BASE (building, antenna, structure, earth) jumpers, criticize the concept, saying it's the most difficult and often the most dangerous kind of parachuting.

One available parachute evacuation system is the Executive Chute, made in the United States by Destiny Aircraft Corporation of Michigan. The chute is deployed by a static line attached to a fixed object in the building to which the evacuee secures the ripcord before jumping, enabling the parachute to open in the event the evacuee freezes or loses consciousness during the jump. The rounded canopy, intended to eliminate the need for steering, should allow evacuees to float straight down after the chute deploys.

The chute can be used at any height above 12 stories, or 125 feet (38 meters), and must be inspected and repacked every 3 to 5 years.

Although about 200 Executive Chutes have been sold, mainly to private individuals, there's no documented use of them during a high-rise emergency.

Another parachute, the U.S.-made Evacuchute by Emergency Evacuation Systems, is also designed for hands-free, static-line deployment, but its cone-shaped canopy, which adds stability, allows the user to steer it away from a building. When stored properly, it's designed to last 15 years. Annual inspection and repacking are required. The Evacuchute is recommended for use at any height above 14 stories, or 140 feet (43 meters).

The Evacuchute has been commercially available since July 2002.

Regulatory and listing issues
Should the industry decide to pursue the use of unconventional emergency evacuation systems, developing regulations governing them will be challenging for a variety of reasons. Such regulations will have to acknowledge that controlled-descent devices are last resorts, to be used only when conventional exits are no longer available, serviceable, and useable. They will also have to address significantly different expectations about the conditions and risks under which these systems will be used.

Precedent for the use of unconventional approaches already exists in Sections 7.2 and 7.2.10 of NFPA 101. Section 7.2.10, entitled "Slide Escapes," specifically recognizes slide escapes as a means of egress when permitted in Chapters 12 through 42 of NFPA 101. (Note 3) Section 7.2.10 also states that slide escapes must be of an approved type and that the rated capacity of such slides must be taken into account in overall egress planning.

Chapter 40, "Industrial Occupancies," allows slides to be used for 100 percent of the emergency exiting capacity of high-hazard occupancies, but only when potential evacuees are regularly trained in their use. And Appendix A.11.2.2 notes that escape chutes, controlled descent devices, and elevators "should not be substituted for the provisions of this Code."

UL has already listed some unconventional controlled descent devices and components, which are thus subject to ongoing inspection programs to maintain those listings. However, UL's documentation notes that the devices have been evaluated for mechanical operation only and are not intended for use as a means of egress during fires. The evaluations conducted to date address only specific properties, such as rate of descent speed, capacity, and durability or resistance to corrosion.

 Interestingly, the regulatory situation surrounding controlled-descent devices appears similar to that associated with previous unsuccessful attempts to develop standards for escape hoods, which were the subject of intense debate on the floor of NFPA meetings in 1998 and 1999.

Human factors
Perhaps the most pressing questions the industry would have to answer before unconventional descent devices became conventional have to do with the users, not the equipment or the regulations governing it. The technical and engineering aspects of the controlled-descent systems currently available appear reasonable, but their wholesale application to potentially large numbers of people represents an untried concept in the United States. In fact, relying on such equipment is contrary to everything we currently understand about the interaction between human behavior and building performance.

 The effect on evacuees of these unconventional evacuation methods would have to be studied, as would methods for coping with anxiety about using such systems in general. Current research on the use of elevators during high-rise emergencies is causing anxiety in the fire protection community, not only about the performance of the equipment, but about the anticipated responses of building occupants as well. And high-rise occupants use elevators every day. How much greater might be their fear of using an unknown device in trying circumstances?

In addition, users would have to be trained and the equipment maintained regularly if it were to be effective in an emergency. And the strengths and weaknesses of each system would have to be carefully assessed before it could be put into the field, especially into existing structures that weren't designed with their use in mind. Other issues that might affect their use, such as cross winds, would have to be evaluated as well.

Will these unconventional exiting systems become accepted tools, available to building designers, regulators, first responders, and occupants? Perhaps.

Enhancements to building performance in the coming years will certainly entail another look at non-traditional means of building evacuation. Broader use of elevators for evacuation, simultaneous evacuation of all floors in a high-rise, new ways of evacuating occupants with mobility impairments, and use of unconventional systems are all open for discussion.

First responders already use some of the systems described here, and their use in high-hazard occupancies or tall towers with limited numbers of occupants—especially those who are physically fit—may be reasonable. But developing codes and standards to address their performance and introducing them to building occupants will present extraordinary challenges.

Dr. Joseph Zicherman is Principal, IFT/Fire Cause Analysis Inc., Point Richmond, California.

References

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• Alvares, Kanury, Wiersma, and Pefley, "Firesafe Sanctuaries for High-Rise Structures," Fire Technology, Vol. 11, No.4 (November 1975), pp. 241–254.
• Smith, Ray A., "The Property Report: High-Rise Is Aflame, Stairwells Are Blocked—What Now?" The Wall Street Journal, 21 August 2002, B1.
• Zicherman, Joseph, Editor, Fire Safety in Tall Buildings, Council on Tall Buildings and Urban Habitat, New York: McGraw Hill, 1992.
• Kendik, Ezel, "Determination of the Evacuation Time Pertinent to the Projected Area Factor in the Event of Total Evacuation of High-Rise Office Buildings via Staircases," Fire Safety Journal, Vol. 5 (1983), pp. 223–232.
• Isner, Michael S., "Smoky Fire Kills Four in New York High-Rise," Fire Journal, (September/October 1988), pp. 72–77.
• Galbreath, M., "Canadian Experience of Fire Safety in High Buildings," Fire Safety Journal, Vol. 7 (1984), pp. 87–91.
• Tallmadge, Thomas, Editor, "The Origin of the Skyscaper," Report of the Committee Appointed by the Trustees of the Estate of Marshall Field for the Examination of the Structure of the Home Insurance Building, Chicago: Ralph Fletcher Seymour, The Alderbrink Press, 1939.
• Council on Tall Buildings and Urban Habitat, Building Safety Assessment Guidebook, 2002.
• Tamura, G.T., and McGuire, J.H., "Air Tightness of Fire Dampers for Smoke Exhaust Systems in High-Rise Buildings," ASHRAE Transactions, Vol. 90 (1984), Part 1B, pp. 647–654.
• Lathrop, James K., "Two Fires Demonstrate Evacuation Problems in High-Rise Buildings," Fire Journal, (January 1976), pp. 65–70.
• Bryan, John L., "Chapter 3-12: Behavioral Response to Fire and Smoke," The SFPE Handbook of Fire Engineering, Ed. Phillip DiNenno, Quincy, Mass.: NFPA, 2002.
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• Nelson, H., and Mowrer, F., "Chapter 3-14: Emergency Movement," The SFPE Handbook of Fire Engineering, Ed. Phillip DiNenno, Quincy, Mass.: NFPA, 2002.
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• Bryan, John L., "Human Behavior in the Westchase Hilton Hotel Fire," Fire Journal (July 1983), pp. 78–85.
• Demers, David, Principal Investigator, "Investigation Report on the Las Vegas Hilton Hotel Fire," Fire Journal (January 1982), pp. 52–63.

Notes

1. This subject was addressed in an August 25, 2003 article in The Wall Street Journal.
2. For example, U.S. Patent 4,018,423 protects an "Emergency Decent Device," which apparently was never exploited commercially. 
3. Provisions of Section 7.2.10 also address the need for slide escapes to be of an approved type, implying that testing and listing will be required, and the rated capacity of such slides in overall egress planning. In addition, Appendix A.11.2.2 states, "Escape chutes, controlled descent devices, and elevators are permitted to provide escape routes in special structures; however, they should not be substituted for the provisions of this Code." Section 40. 2.2.11 of Chapter 40, "Industrial Occupancies," allows for the use of slides for 100 percent of the emergency exiting capacity of high-hazard occupancies, but only when their potential users are regularly trained in their use.

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