Restructuring the fire alarm code

NFPA 72-2010 features significant changes to benefit system design and installations.

01/17/2012


Figure 1: Messaging and alert systems can be used to alert those on a campus or other large facility. Courtesy: SiemensWhile the 2010 edition of NFPA 72: National Fire Alarm and Signaling Code has been available since fall 2009, it has been adopted by only a few jurisdictions at this time. Adoption and application of NFPA 72 is typically driven by the model building or fire codes (e.g., International Building Code, Life Safety Code, etc.). Even though the 2010 edition may not yet be enforced in your jurisdiction or on your project, there are a number of significant changes to the code that could help with current system designs or installations.

Just when you had gotten used to the organization of the code (it has been consistent for the 2002 and 2007 editions), the Technical Correlating Committee decided to reorganize the code. In defense of the committee, some changes were necessary to accommodate new criteria for emergency communication requirements, so rather than shoehorn information into the current organization, the committee decided to expand the chapter structure to allow for future inclusion of information and criteria. The goal is to not have to reorganize the code for a long time. The new code structure has four basic sections:

  • Chapters concerned with administration of the code
  • Chapters applicable to all types of systems (support chapters)
  • Chapters addressing requirements specific to fire alarm system type
  • Annexes providing explanatory material and informational references.

While it looks on the surface to be a significant expansion of the code, users will notice that a number of chapters have been reserved for the future.

The last significant code reorganization occurred in the 2002 edition when the document was reorganized to meet the NFPA Manual of Style. The Manual of Style provides for a level of consistency among all NFPA documents. For example, Chapter 1: Administration; Chapter 2: Referenced Publications; and Chapter 3: Definitions will be the same in almost every NFPA code and standard. In the 2010 edition of NFPA 72, Chapters 4 through 9 are identified as “reserved.” This implies that information will be added to these chapters in the future. However, there has not been any discussion at the committee level as to what this information might be. The organization and reservation of chapters were established to provide blocks of 10 chapters for ease of use.

Within the support chapters group, five chapters are currently used. These include Chapter 10: Fundamentals; Chapter 12: Circuits and Pathways; Chapter 14: Inspection, Testing, and Maintenance; Chapter 17: Initiating Devices; and Chapter 18: Notification Appliances. The other chapters within this group—Chapters 11, 13, 15, 16, and 19—are reserved for future use.

The most significant technical changes were made in chapters dealing with specific system requirements. Many of the requirements in Chapter 21: Emergency Control Functions and Interfaces existed in Chapter 6: Protected Premises Fire Alarm Systems of the 2007 edition. Issues addressed in this Chapter 21 include:

  • Elevator recall and firefighter’s service for elevators
  • Elevator shutdown interface with fire alarm equipment
  • Fire alarm interface with elevators used as part of the evacuation scheme for buildings
  • Fire alarm interface with HVAC equipment
  • Fire alarm interface with door releasing service and electric door locks.

Chapter 24: Emergency Communications Systems (ECS) is almost entirely new. This chapter includes the requirements for emergency voice alarm/communication systems but has been expanded to include requirements for the design and installation of all emergency communication equipment, including mass notification.

The final change in the organization of the document is the addition of two new annexes. Annex C: System Performance and Design Guide, is intended to provide additional guidance to designers by identifying various issues and factors that should be considered when designing for large buildings or unusual applications. Annex D: Speech Intelligibility was added to provide guidance on the design, installation, and testing of voice communication systems

The annexes in NFPA 72 provide a significant amount of information that can inform a design as well as provide further clarification to the actual code requirements.

Chapter 12: Circuits and pathways

This new chapter on pathway designations incorporates a number of concepts that were previously addressed in the fundamentals and protected premises chapters of the 2007 edition of NFPA 72. The code requires assignment of class designations to circuits based on their performance characteristics under fault conditions. Over the last several cycles of the code, there have been fluctuations in the designation of circuits. With the expansion of the code to also address other ECS such as mass notification, the technical committee felt that it was necessary to more clearly describe the performance characteristics of all the circuits that could be incorporated into a fire alarm or emergency communication system. Gone are the tables defining performance characteristics of initiating, signaling line, and notification appliance circuits that were in Chapter 6 of the 2007 edition. “Styles” have also been deleted from the body of the code. These designations and their performance characteristics have been maintained in the annex for reference.

Class A and B circuit designations still remain for initiating devices, notification appliance, and signaling line circuits, while a number of new circuit designations have been added to address all types of circuits. Here are all of the various designations for all types of fire alarm circuits and their performance characteristics:

Class A

  • Includes a redundant path so signals can be sent in either direction
  • The circuit is able to operate with a single open
  • Any condition that affects the intended operation of the circuit is annunciated as a trouble
  • This designation is typically applied to initiating devices, notification appliances, and signaling line circuits.

Class B

  • The circuit does not include a redundant path
  • Devices located beyond an open in the circuit cannot report to the panel
  • Any condition that affects the intended operation of the circuit is annunciated as a trouble
  • This designation is typically applied to initiating devices, notification appliances, and signaling line circuits.

Class C

  • These are pathways that are monitored for their ability to perform through end-to-end verification
  • If communication between devices and the panels is not verified, the lack of communication is annunciated as a trouble
  • This designation has been added to address communication between a fire control unit (or supervising station) and wired or wireless LANs or WANs. This could also apply to the pathway between a digital alarm communicator transmitter and the public switched telephone network.

Class D

  • This designation is for circuits that are designed to be fail-safe. Take, for example, a power circuit energizing door hold open device. If that circuit breaks and the doors fail closed (assuming that is the “safe” condition), the circuit is designated as Class D.
  • Opens in these types of circuits are not required to annunciate.

Class E

  • This designation is for circuits that are not required to be monitored for integrity. NFPA 72 specifically identifies pathways that are not required to be monitored for integrity in Section 10.17: Monitoring Integrity. An example of a circuit that is not required to be monitored is the conductors in conduit between enclosures of control equipment that are located within 20 ft of each other.

Class X

  • Circuits with this designation have the same performance characteristics as Class A circuits but are also required to perform with a single short circuit
  • Class X circuits perform with the same characteristics as circuits previously designated Class A, Style 7.

Pathway survivability

Figure 2: Mass notification systems are common on large college or university campuses. Courtesy: SimplexGrinnellSurvivability has been a requirement of NFPA 72 in previous editions for circuits and equipment required for the performance of voice equipment used for relocation or partial evacuation of occupants. The 2010 edition takes a different approach. The code now identifies different levels of survivability, and the use of the equipment drives the required level of survivability. The highest levels of survivability may only be required based on a risk analysis. Here are the different levels of pathway survivability:

Pathway Survivability Level 0: This level does not impose any additional criteria for survivability beyond the requirements of NFPA 70: National Electrical Code that would be applicable to the installation of the type of circuit.

Pathway Survivability Level 1: In buildings having full sprinkler protection in accordance with NFPA 13: Standard for the Installation of Sprinkler Systems, circuits run in metal raceways meet this level of survivability.

Pathway Survivability Level 2: This level of survivability requires either pathways that are protected by 2-hour fire-rated construction or cables that are inherently 2-hour-rated.

Pathway Survivability Level 3: This level of survivability requires compliance with the criteria of Level 2, and be in a building having a sprinkler system installed in accordance with NFPA 13.

Chapter 23: Protected Premises Fire Alarm Systems requires that a voice system used for relocation or partial evacuation of occupants be designed so that a fire within a single notification zone does not impair the ability of the system to operate in other notification zones. The code does not identify a specific pathway survivability level in this case.

Chapter 24 specifies pathway survivability levels under certain circumstances. When ECS are used for partial evacuation or relocation, Chapter 24 requires the pathways to be designed to meet Level 2 or Level 3 survivability. Chapter 24 criteria for other types of systems are noted here:

  • Pathways for mass notification systems (MNS) are allowed to be Level 0 or higher based on a risk analysis.
  • Two-way ECS are required to be designed as survivability Level 2 or 3.
  • Area of refuge two-way communication systems are required to be designed as Survivability Level 2 or 3.

Intelligibility

The subject of intelligibility of voice systems has been intensely debated by the NFPA 72 Technical Committees over the last decade. Many people in the industry erroneously believe that intelligibility of voice systems is a recent requirement in NFPA 72.

The requirement that voice instructions be intelligible was first codified in the 1999 edition of NFPA 72. Intelligible voice was defined as audible voice information that is distinguishable and understandable. While the 1999 edition was the first to include this requirement, the ability to understand voice messages has always been a factor in system acceptance.

The development of intelligibility measurement tools that are readily available (albeit expensive) and usable by people, other than acousticians, has fostered some of the misconceptions.

At the onset of the code development cycle for the 2010 edition of NFPA 72, there was a desire from technical committees to incorporate specific requirements for intelligibility of voice communication that would require quantitative measurement of all voice systems. The Fire Protection Research Foundation, an independent, nonprofit organization whose mission is to plan, manage, and communicate research in support of the NFPA, organized a project with a goal of establishing a basis for code development in the area of intelligibility testing. The final report, “Intelligibility of Fire Alarm and Emergency Communication Systems,” was published in November 2008. The project resulted in the development of guidelines for performing quantitative intelligibility testing that have been incorporated in the new Annex D. These guidelines identify issues and challenges with designing for intelligibility. Designers of fire alarm and MNS should take these guidelines into consideration.

Chapter 18: Notification Appliances has incorporated a number of changes to clarify the intent of the code relative to intelligibility. First, quantitative measurement for intelligibility is not required by NFPA 72 under any circumstances. The definition of “intelligible” has been revised to read: “Capable of being understood; comprehensible, clear.” In the event that there is a dispute between a designer and an authority having jurisdiction, the quantifiable methods of measurement described in Annex D can be used to measure intelligibility. There also is nothing to preclude an owner from specifying a certain level of intelligibility, but that should be done through a specification.

Secondly, Chapter 18 incorporated the concept of acoustically distinguishable spaces (ADS). An ADS is defined in NFPA 72 as “An emergency communication system notification zone, or subdivision thereof, that might be an enclosed or otherwise physically defined space, or that might be distinguished from other spaces because of different acoustical, environmental, or use characteristics, such as reverberation time and ambient sound pressure levels.”

The designer is responsible for identifying the ADS in a building and also identifying those that are required or not required to be provided with intelligible voice. The code intent here is to recognize that some areas of a building will have less than perfect intelligibility. Examples of such spaces are parking levels and large volume spaces. Due to the hard surfaces and challenging acoustic characteristics, intelligibility throughout these areas cannot be reasonably achieved. An occupant may have to move toward a speaker to be able to understand a message. Given the fact that messages and alarm signals are required to be repeated, this is a reasonable approach.

Chapter 24: Emergency communication systems

Figure 3: Chapter 21: Emergency Control Functions and Interfaces helps define what must be included in a building’s fire protection system control panel. Courtesy: Edwards UTCOne of the most significant changes in the 2010 edition of NFPA 72 is the incorporation of design, installation, and testing requirements for MNS into the body of the code. These requirements are located in Chapter 24. 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.

Risk analysis: basis of design: Prior to beginning the design of an MNS, a risk analysis must be completed. A risk analysis is a process used to characterize the probability and potential severity of incidents associated with natural or manmade disasters or other events requiring emergency response and is intended to prioritize those events in the context of all foreseeable emergencies.

The analysis must identify when the system will be required to operate (i.e., before, during, or after an event). The performance needs may drive certain survivability requirements that may lead to requiring a specific survivability level defined in Chapter 12 of NFPA 72.

Another important consideration when designing an MNS is deciding the priority of signals. The 2010 edition acknowledges that signals other than fire alarm signals may take priority over a fire alarm signal when based on a risk analysis.

One-way emergency communications: Prior to the incorporation of mass notification in NFPA 72, fire alarm systems generally have only been allowed to provide occupant notification of fire events. With the expansion of the scope over the last two code cycles, NFPA 72 now addresses emergency communications in a much broader way. This is evidenced by the name change to the title of the standard to the National Fire Alarm and Signaling Code.

Within NFPA 72, criteria for ECS design and installation are broken down to address systems in buildings, wide area notification, and distributed notification.

Systems in buildings: Section 23.9: In-Building Emergency Voice/Alarm Communication System contains familiar requirements for voice fire alarm systems. A majority of these requirements are currently located in section 6.9 of the 2007 edition. The requirements continue to include the provisions applicable to relocation and partial evacuation strategies.

The in-building MNS section provides requirements for a stand- alone MNS or one combined with the fire alarm system. MNS could provide voice messages that are prerecorded for specific events or live voice from a centralized location or specific to the building.

When a visual notification appliance is solely used for mass notification, the lens is typically specified to be amber in color. If the visual notification appliance serves multiple purposes, the color needs to be coordinated with the facility’s emergency plan.

Wide area systems: Wide area MNS provide notification to a large area of a population such as the exterior areas of a college campus or a portion of a city or town. Examples of wide area notification system include sirens for tornado warnings, chemical release warning systems, and sirens signaling industrial plant emergencies. The communities of occupants affected by these systems must be made aware of the signals and must be trained to take appropriate action.

Distributed recipient notification: In addition to in-building and wide area notification, distributed recipient MNS such as e-mails, text messages, and pagers may be incorporated into the MNS. Where a distributed recipient MNS feature is used, the equipment is required have backup equipment and be located behind a system firewall to maintain the integrity of the network.

Two-way emergency communications

The current requirements for two-way communication service currently found in Section 6.10.1 of NFPA 72 have been moved to Chapter 24. Under the new two-way telephone requirements, all telephone circuits must 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 bi-directional amplifiers, 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.

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. These 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 offsite to a supervising station, 9-1-1 center, or other approved monitoring location.

NFPA 72 continues to evolve to address new technologies and applications for fire alarm and ECS. The acceptance and widespread application of the code is a testament to the scores of dedicated professionals who serve on the nine technical committees that make up the project and numerous task groups as well as the organizations that support them.

Grill is a principal with Arup and a past chair of the Technical Committee on Fundamentals of Fire Alarm Systems. He currently serves as chair of the Technical Committee on Notification Appliances for Fire Alarm Systems. He is a member of the Consulting-Specifying Engineer editorial advisory board.



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