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One of the first things you discover when reading NFPA 72 (2010), the National Fire Alarm and Signaling Code, is the interdependence of the chapters. For example, you will find the application, installation and performance requirements for emergency communications systems and their components in Chapter 24. But by itself, this chapter does not cover every aspect of installing such systems.
A requirement unique to emergency communications systems includes pathway survivability. Fire alarm installation stakeholders—owners, designers, contractors and code enforcement officials—often misunderstand this, believing it relates to the reliability of the equipment or the manner in which a contractor installs the fire alarm wiring. Also, the code does not specifically define the term.
However, even though the code does not define “survivability” in Chapter 3, paragraph 23.10.2 states, in part: “Fire alarm systems used for partial evacuation and relocation shall be designed and installed such that attack by fire within an evacuation signaling zone shall not impair control and operation of the notification appliances outside the evacuation signaling zone.” This constitutes the performance definition of “survivability.”
Chapter 12 describes each level of pathway survivability and offers options for the designer and installer to meet the survivability requirements. In the past, some confusion existed where users assumed that any circuit enclosed in a raceway automatically had an acceptable level of survivability. Wire or cable in a raceway certainly has mechanical protection. But, raceway does not provide sufficient protection against the impact from the heat generated by a fire. To remedy the misunderstanding, stakeholders must develop a holistic understanding of all the relevant requirements.
First of all, the entire fire alarm system installation must meet the requirements of NFPA 70 (2008), the National Electrical Code. Next, the installation must meet the requirements found in the various chapters of NFPA 72 (2010), which outlines four levels of survivability in Chapter 12:
• Level 0 designates circuits or pathways that do not require survivability.
• Level 1 designates those pathways installed in buildings fully protected by automatic sprinkler systems in accordance with NFPA 13, Standard for the Installation of Sprinkler Systems, with any interconnecting conductors, cables, or other physical pathways installed in metal raceways.
• Level 2 designates pathway survivability that becomes more complicated and consists of one or more of the following: two-hour fire-rated circuit integrity (CI) cable; two-hour fire-rated cable system [electrical circuit protective system(s)]; two-hour fire-rated enclosure or protected area; two-hour performance alternatives approved by the authority having jurisdiction (AHJ).
• Level 3 designates pathways in buildings fully protected by an automatic sprinkler system in accordance with NFPA 13, Standard for the Installation of Sprinkler Systems, that also meet one or more of the four methods of survivability outlined in Level 2.
When installing circuits or pathways that require survivability, the designer must identify the interconnections and survivability levels on the drawings.
Having set the stage for the survivability requirements, we can refer to the emergency communications systems chapter of NFPA 72 (2010) for when communications circuits must have survivability.
The first type of fire alarm system that requires survivability includes the typical high-rise in-building fire emergency voice/alarm communications system. This system normally employs occupant relocation or partial evacuation. Because of this feature, the circuits and pathways must have a Level 2 or Level 3 pathway survivability. In this case, the pathway survivability requirements apply to notification and communications circuits, and to other circuits necessary to ensure the continued operation of the emergency communications system.
A new survivability requirement appears in the 2010 edition of the code. This requirement applies to the separation of the in-building fire emergency voice/alarm control equipment. In addition to the required pathway survivability, the code now requires that where the circuits run through junction boxes, terminal cabinets or control equipment—such as system control units, power supplies and amplifiers—and where such equipment does not maintain cable integrity, these components must also use one of the following methods: a two-hour fire-rated enclosure; a two-hour fire-rated room; and other equivalent means to provide a two-hour fire-resistance rating approved by the AHJ.
Other emergency communications systems that will require a pathway survivability Level 2 or 3 include the following:
• Two-way in-building wired emergency communications systems
• Two-way radio communications enhancement system, exclusive of the antennae, used in lieu of a two-way in-building wired emergency communications system
• Area of refuge emergency communications systems
The code will allow less stringent pathway survivability requirements if the designer or contractor supports those requirements by conducting a risk analysis. You should know the performance definition of survivability and how to ensure you meet the relevant requirements.
MOORE, a licensed fire protection engineer, frequent speaker and an expert in the life safety field, is a past chair of the NFPA 72 Technical Correlating Committee. Moore is a principal with Hughes Associates, Inc. at the Warwick, R.I. office. He can be reached at [email protected].