Emergency communications systems and NFPA 72-2010
Over the past two years, the technical committees responsible for NFPA 72 have been hard at work developing the 2010 edition of the National Fire Alarm Code . The 2010 edition will be put before the NFPA membership at the NFPA Conference & Expo in Chicago this June.
The 2010 edition of NFPA 72 will have undergone significant changes from the 2007 edition, including the addition of three new chapters and a name change to National Fire Alarm and Signaling Code. One of the most significant changes is the incorporation of design, installation, and testing requirements for mass notification systems into the body of the code. These requirements will be in a new chapter called Emergency Communications Systems (ECS). Another facet of this change is the relocation of other emergency communication requirements of Chapter 6 in the 2007 edition to the new chapter on ECS.
The development process of the new chapter began when the NFPA Standards Council created a new technical committee on emergency communications within the Signaling Systems Project. The new technical committee began with 12 principal members and grew to 29 principal members at the conclusion of this code development cycle. The committee integrated existing requirements in NFPA 72 on emergency communications, transformed Annex E of the 2007 edition to code language, considered criteria of other references on mass notification (e.g., Unified Facilities Criteria (UFC) Design and O&M: Mass Notification Systems (UFC 4-021-01)), and considered numerous public proposals and comments during the development of the new chapter on ECS.
The new ECS chapter is subdivided into four major sections, one-way communication, two-way communication, command and control, and performance-based design. Figure 1 shows how the new chapter is organized.
Risk analysis—basis of design
Prior to beginning the design of a mass notification system, a risk analysis must be completed. The preparation of a risk analysis will be a requirement of the 2010 edition of NFPA 72. A risk analysis is a process used to characterize the probability and potential severity of incidents associated with natural or man-made disasters or other events requiring emergency response. The designer must consider both fire and nonfire emergencies when determining the required performance of the mass notification system and how various signals are handled. The risk analysis will provide the basis for developing the emergency response plan and the design of the emergency communications system. Existing facilities that have an emergency response plan should update it to recognize the emergency communication system and current risks.
The risk analysis process identifies the types of expected emergency events and provides a basis for how they should be handled. This process may require a threat and vulnerability survey to understand and identify the risks. Once the risks have been identified, the urgency of the potential event must be considered. For example, a chemical release could pose an immediate threat to an identified geographic area; a hurricane moving on a specific track would rank as a lower priority.
The analysis must identify when the system will be required to operate before, during, or after an event. The performance needs may drive certain survivability requirements. The circuits may need to be fire-rated cable or be installed in underground hardened ducts to survive the expected conditions. A new Circuits & Pathways chapter in the 2010 edition of NFPA 72 will provide survivability requirements that can be incorporated in specifications and designs. In addition to the circuit survivability, the facility that functions as the central control station and equipment must be designed to maintain functionality identified by the risk analysis.
One-way emergency communications
Prior to the incorporation of mass notification in NFPA 72, fire alarm systems generally have been allowed only to provide occupant notification of fire events. With the expansion of the scope over the past two code cycles, NFPA 72 now addresses emergency communications in a much broader way.
In the 2010 edition of NFPA 72, emergency communications systems are defined as systems for the protection of life by indicating the existence of an emergency situation and communicating information necessary to facilitate an appropriate response and action. This definition demonstrates that what was once a standard focused primarily on protection of life and property has been significantly expanded.
Within NFPA 72, criteria for emergency communications systems design and installation are broken down to address three specific areas:
Systems in buildings
Systems in buildings
The In-Building Emergency Voice/Alarm Communication System section contains familiar requirements for voice fire alarm systems. A majority of these requirements currently are located in NFPA Section 6.9 of the 2007 edition. The requirements continue to include the provisions applicable to relocation and partial evacuation strategies.
The In-Building Mass Notification Systems section provides requirements for a stand-alone mass notification system or one combined with the fire alarm system. Mass notification systems provide prerecorded voice messages for specific events or live voice messages from a centralized location or specific to the building.
When a visual notification appliance is used solely for mass notification, it must be amber in color. If the visual notification appliance serves multiple purposes, the color must be coordinated with the facilities emergency plan.
Wide-area mass notification systems provide a notification to a large area of a population, such as the outdoor areas of a college campus or a portion of a city or town. Examples of currently used wide-area notification system include sirens for tornado warnings, chemical release warning systems, and sirens signaling nuclear power plant emergencies. The communities of occupants affected by these systems must be made aware of the signals and be trained to take appropriate action.
Newer technology includes high-powered speaker arrays where voice messages or tones can be remotely broadcast to a specific area to provide information before, during, and after an incident. A high-powered speaker array could be used on a college campus to direct staff and students away from danger such as a gunman or a bomb threat. The code requires the speaker arrays to be arranged in a manner to provide intelligible voice and audible tone communications in accordance with the Notification Chapter requirements.
The equipment and supporting structure must be designed to operate in the event of an emergency to meet the structural, wind, and seismic loads that are identified by the risk analysis. Power supplies for wide-area notification speaker arrays must be designed to provide seven days of standby followed by 60 min at full load.
Distributed recipient notification
In addition to in-building and wide-area notification, distributed recipient mass notification systems such as e-mails, text messages, and pagers may be incorporated as part of the system. Where a distributed recipient mass notification system feature is used, the equipment must have backup equipment located behind a system firewall to maintain the integrity of the network.
Two-way emergency communications
The current requirements for two-way telephone communications service in NFPA 72 Section 6.10.1 have been moved to the new ECS chapter. New two-way telephone requirements include requiring five telephone circuits to be common talk, and specific locations have been identified to coordinate with the expansion of radio communication enhancement systems.
Two-way radio communications enhancement systems commonly referred to as bidirectional amplifiers or repeaters are replacing the firefighter telephones in many jurisdictions to improve fire ground communications within a building. The criteria for these systems were expanded during the 2010 cycle.
The new requirements include definition of the extent of radio coverage within a building. Radio coverage is required for 99% of the floor area in critical areas such as emergency command centers, fire pump rooms, exit stairs and passageways, elevator lobbies, standpipe connections, sprinkler system control valves, and other areas deemed critical by the authority having jurisdiction. These areas were required to be provided with a firefighter telephone. In addition, radio coverage must be provided to 90% of the general floor area of the building. Radio enhancement communication systems also are required to provide supervisory and trouble signals for the signal booster and power supplies. These signals would be monitored by the fire alarm system.
Criteria for the two-way communication systems required by building codes for areas of refuge have been incorporated into the code. These systems provide communication between the area of refuge and a central control point. Such systems can be stand-alone or integrated with the fire alarm system. If there isn’t a staffed central control point, the system can communicate off-site to a supervising station, communications center, or other approved monitoring location.
The control of the emergency communications system must be coordinated with the emergency response plan. The emergency response plan can be developed through the application of NFPA 1600 Standard on Disaster/Emergency Management and Business Continuity Programs and NFPA 1620 Recommended Practice for Pre-Incident Planning .
The central control location may be a single location or multiple locations where the mass notification system is operated. Depending on the notification area, multiple central control locations may be required so that a control facility is available during events identified during the risk analysis. With an increased number of control locations that may have the ability to disable fire alarm notification to occupants or direct people to an area of danger, security is an important design element of each of the control locations.
Another important section of the new ECS chapter is the performance-based design section. This section provides flexibility in the design of an ECS. Following the general structure found in NFPA 101 and NFPA 5000, this section outlines the methodology for developing a performance-based design of a mass notification system. It also provides the general goals and objectives for the system.
The design team, which includes not only the design professional but also the owner (or its representatives) and the authorities having jurisdiction, must work together in a collaborative process to make sure the system will meet specific goals and objectives as defined by the risk analysis.
The selection of the design team is an important step before beginning the risk analysis. Communication and coordination between and among the various members of the design team is an important element in achieving system performance goals.
During the design process of a mass notification system, it is important that all other systems integral to or necessary for proper performance of the system be coordinated. The programming of these systems must be integrated with the emergency response plan and coordinated with the sequence of operations for all of the systems. Some distributed recipient notification systems such as text messaging or e-mail may provide conflicting information such as a text message directing a person to remain in place, while the fire alarm system in the building provides the evacuation message. If the fire alarm evacuation system activated before the occupants received the message, there could be confusion. It is important that delays in transmission of signals be considered and minimized for critical information.
Another important consideration is prioritizing signals in certain situations, such as when the fire alarm notification system is overridden by a higher priority message. The latest edition of NFPA 72 acknowledges that signals other than fire alarm signals may take priority over a fire alarm signal. During the development of the emergency response plan, it is important to determine if notification and prioritizing signals should be handled automatically or with manual intervention from trained staff at a central control station. If automatic prioritization is necessary, the fire alarm system may have to be integrated with chemical, biological, radiological, nuclear, or gunshot detectors. With the increased complexity of the system, there will be an increased need to test the system, including the employment of knowledgeable resources to confirm that the system is operating correctly.
While the need for survivability and level of survivability should come out of the risk analysis, survivability requirements have been relocated to a new chapter that defines specific levels of survivability. Some have argued that the new chapter will make it easier for a designer to require a specific survivability level and simplify the specification process, but the proof will be in the application of the code.
Where cable survivability of a circuit was required by the 2007 edition, the cables were permitted to be installed in metal raceways in a sprinklered building as an alternative to a two-hour rated cable, cable system, or enclosure. The 2010 edition has removed the method that permitted metal raceway and sprinklers as an alternative to a 2-h rated system.
|Woodward is a fire engineer with Arup Fire in Cambridge, Mass. He is a principal member of the NFPA technical committee on ECS. Woodward specializes in performance-based design solutions and code consulting. Grill is a principal with Arup Fire, where he focuses on fire protection engineering. He is a member of Consulting-Specifying Engineer’s editorial advisory board and a past president of the Society of Fire Protection Engineers.|
Intelligibility of ECS
Standard methodologies for quantitatively measuring intelligibility have been around for some time. The idea of quantitatively measuring fire emergency voice evacuation communication was first introduced in the 1999 edition of NFPA 72. There were proposals to require a specific measured intelligibility of 0.7 on the common intelligibility scale (CIS) for the 1999 edition, but the NFPA membership rejected the incorporation of the requirement in the code. The Annex to the 1999 edition provides guidance for those wanting to perform quantitative measurement of intelligibility and references IEC 60849, sound systems for emergency purposes, published by the International Electrotechnical Commission.
Over the course of the past three code development cycles, this issue has been regularly debated. These debates have included anecdotal information regarding a number of voice evacuation systems that have been quantitatively tested for intelligibility. The authors also have been involved in a number of intelligibility tests.
At the onset of the development cycle for the 2010 edition of NFPA 72, there was a desire by many on the technical committees to incorporate specific quantitative requirements for intelligibility of voice communication, which would require quantitative measurement of all voice systems. The Fire Protection Research Foundation organized a project with a goal of establishing a basis for code development in the area of intelligibility testing. The project resulted in the development of guidelines for performing quantitative intelligibility testing that will be included in the annex to NFPA 72. These guidelines identify issues and challenges with designing for intelligibility. Designers of fire alarm and mass notification systems should take these guidelines into consideration. The final report is available through the foundation and can be downloaded from the NFPA Web site.
The work of the Fire Protection Research Foundation regarding intelligibility received significant review during the development of language for the 2010 edition of NFPA 72. A number of Technical Correlating committee Task Groups were developed to dissect the work with the goal of creating appropriate code requirements.
While everyone involved believed that voice communications systems should be intelligible, the need for quantitative measurement of all systems was heavily debated. The environment in which the voice communication system must perform has a significant impact on the ability to perform. The acoustic characteristics of the space or area must be taken into consideration during the design process. The acoustics also can change significantly before and after occupancy of the space and over time.
The committees finally settled on continuing to require voice systems to be intelligible, while reinforcing that for a system to be considered to produce intelligible voice, the communications need to be understandable. This allows for the continuation of the method that is currently often used for testing intelligibility—the “walk around and listen” method. The annex to NFPA 72 will provide the methodology for the quantitative measurement of intelligibility for more acoustically challenging spaces or where it may be required by a specification or owner.