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VENUE READY FOR AN INCIDENT?
By Robert Sedlak, P.E. and Alan Traugott
In the event of the unthinkable--a terrorist makes it through the security measures put in place--the reliability of the life safety systems and a well defined Emergency Action Plan are critical to safely evacuate the building. The Life Safety Systems in buildings are typically designed based on local building code requirements, which assume a fire that starts and grows from initial fuel sources inside the facility. Normally Life Safety Systems are designed taking into account the types of sources and the fire load present. It is generally assumed that the sprinkler system will operate and contain a fire or slow its growth, smoke control systems will maintain a safe means of egress and alarm systems will properly provide warnings allowing occupants to safely exit the building. A terrorist event is a far different scenario. Bomb blasts quickly cause widespread fire, damage, and large amounts of smoke, which can potentially overwhelm a properly functioning Life Safety System. To further complicate the issue, it is possible that some of the Life Safety System might be damaged during a bomb blast, thereby hindering a safe evacuation.
A biological or chemical terror threat presents an entirely different situation, since the threat may not be immediately detected. The most likely target is the HVAC system, in which a biological or chemical agent is released into the air stream prior to or during an event. However, food storage and distribution systems, as well as water systems, are also potential targets. Since it is technically challenging and costly to retrofit system components that will detect and mitigate these threats in real time, the best solution for existing facilities, at the moment, is prevention through stringent security measures and procedures. These were discussed in detail at the recent IAAM Crowd Management conference in San Diego. New facilities, going forward, can more cost effectively incorporate design changes to enhance security from biological and chemical terror.
Our focus, as building systems engineers, is to enhance the reliability of the building systems, and in particular the Life Safety systems. However, it should also be recognized that “best practices” will continually evolve as the industry and government agencies race to understand and respond to the nature of the new threats and as codes adapt to new life safety concerns. This article will primarily deal with Life Safety systems hardening in response to the potential impact of bomb blasts.
In evaluating the potential impact of a bomb blast on the building’s life safety systems, it is necessary to understand the nature of the threat and the vulnerabilities of the building. Truck bombs that are driven into the loading dock, parked adjacent to the building, or driven onto the event floor have different implications than a bomb that can be carried in to any part of the building by an individual. Blast consultants and structural engineers can help to identify the impact to a building’s structure and facade for different size and locations of bombs.
The following discusses the typical Life Safety System in the building and potential points of failure that merit consideration. Some of the situations considered below can be mitigated by the proper blast protection or strategically locating system components in the building away from areas identified by the blast consultant as susceptible to damage.
FIRE ALARM SYSTEM
– The Fire Alarm System is required to notify the local fire department,
initiate proper evacuation alarms, communicate with occupants, and activate
automatic HVAC system sequences, including smoke control. This processing
function generally comes together at the Fire Command Center. Should a bomb
blast damage the Fire Command Center or the main Fire Alarm wiring serving
the system, the fire department or facilities personnel or the system itself
will be unable to determine the extent of the damage. Further, the Fire
Alarm communication systems could not be used to communicate with building
occupants on how best to evacuate. In addition, the smoke exhaust system
that is designed to keep the egress path clear of smoke may not activate.
SPRINKLER/STANDPIPE SYSTEM – The sprinkler system is the first line of defense in controlling a fire after a blast. However, sprinkler systems are generally designed with a rate of water flow that will serve a zone of 1,500 square feet at a time. In a bomb blast situation, the area affected could easily exceed 1,500 square feet, and as such would overwhelm a code compliant sprinkler system. In addition, many sprinkler pipes would likely be damaged by a blast, causing the sprinkler system to be inoperative in the affected area.
To further complicate the situation, most sprinkler systems have been combined with the building standpipe system. The standpipe system water supply is used by the fire department to connect their hoses to fight a fire. The damaged sprinkler piping would also make the standpipe system inoperative until the proper valves can be shut down to isolate the systems.
Both the standpipe and sprinkler systems generally share common distribution piping, supply piping and pumps at the lowest level. Damage to any of these common elements can render the entire system non-functional.
Consideration should be given to the following:
EMERGENCY POWER - The most critical element in keeping the Life Safety Systems operational is power. It is possible or even likely that a bomb blast will knock out the utility power serving the building. This will leave the emergency generator as the source of power to operate smoke exhaust fans, fire pumps, emergency lighting, elevators, fire alarm system, and the public address system.
One of the major issues associated with the reliability of the emergency power system is the location of the emergency generator. Since the generator needs cooling air and combustion air, it is generally located at the exterior of the building. The louvers used by the generator make it impossible to blast-protect the room. Possible solutions include locating the generator in protected areas or using a combination of remote radiators and air conditioning to eliminate the intake louvers. Another solution might be to provide redundant generators at opposite ends of the building.
Further complicating the hardening of the emergency power system is the network of emergency power distribution, which runs throughout the building. The following approaches should be considered:
SMOKE EXHAUST – Most enclosed venues have a smoke exhaust system to keep egress paths clear of smoke. These systems are designed based on a fire size that is consistent with the venue’s fuel load. In most cases, a five mega-watt fire is used in design, which is approximately equivalent to a large fiberglass boat burning. The objective of the smoke exhaust system is to maintain a clear egress path long enough for occupants to evacuate. It is likely that these systems would also be overwhelmed in the event of a bomb blast. The installation of additional fan capacity or emergency roof hatches should be considered.
Even if additional capacity is not added to the smoke exhaust system, during an emergency, some smoke exhaust is better than none. Issues to be considered in the reliability of the smoke exhaust system include:
SOUND SYSTEM – The sound system is used in most venues for occupant notification. During an emergency condition, the fire alarm system interfaces with the sound system to provide automatic and/or manual verbal notification. The following items need to be addressed:
EMERGENCY LIGHTING – Should the power fail during an emergency condition, operational emergency lighting is imperative to minimize panic, as well as to allow occupants to find a safe means of egress. As with the sound system, the emergency lighting system has many of the same interfaces with the fire alarm and emergency power system that must be functional in order for the system to operate. The following issues should be addressed to enhance reliability, including:
SCOREBOARD – Some buildings use scoreboards to provide visual alarm indication to patrons. As with the other systems, it is vital that the fire alarm system, emergency power and inter-connecting wiring remain functional. In addition, the equipment that controls the scoreboard must be in a protected location.
EMERGENCY COMMUNICATION – During an emergency, it is likely that normal phones will be knocked out, cell phone networks will be overloaded, and police fire, EMS radios may not work in the building. Consideration should be given to:
SECURITY SYSTEMS - Security systems may not be of much use after an incident, but consideration should be given to hardening the videotape area so that images are preserved for later investigation.
Numerous systems integrate to form a reliable life safety system in buildings. The reliability of these systems must be evaluated based on the new threats which became evident after 9/11/01.
Robert Sedlak, PE, is senior vice president, and Alan Traugott is principal and director of new business, at Flack + Kurtz Consulting Engineers Inc. LLP. They are based in New York City and can be reached at 212/532-9600, or visit their web site at www.fk.com.
International Association of Assembly Managers