Alerting the Masses

Mass notification systems (MNS) are a hot topic in life safety, especially in the educational environment. Although the Army first had the idea of incorporating mass notification into NFPA 72 due to heightened security risks, recent incidents have rapidly expanded interest in MNS on school campuses.

The 2010 edition of NFPA 72, National Fire Alarm and Signaling Code, includes a new chapter on emergency communication systems (Chapter 24) that provides requirements for all types of emergency communications systems, including mass notification. In the 2007 edition, wording was added to allow the use of fire alarm emergency voice-alarm communication systems to be used as part of the MNS. Annex material provided more information.

The new Chapter 24 goes well beyond that. Although model building or fire codes do not require MNS, it is important to set some guidelines to be used when these systems are designed and installed. Each system may contain different components, but all must work properly when needed. It is important to not only be able to determine the threat, but to be able to transmit information quickly and accurately. MNS can be used for many applications, including security and weather-related threats.

Since the 2010 NFPA 72 is now called the National Fire Alarm and Signaling Code, it was necessary to restructure the code to make it easier for nonfire alarm users to locate requirements. It has grown from 11 chapters to 29, although only 14 now are used. The rest are reserved for further subdivision of information and new topics.

The goal is to make the code easier to use. Of the three new chapters, two contain new information. The other one simply relocated existing information from the protected premises chapter into a separate one. There is a new chapter on circuits and pathways (Chapter 12) that describes the requirements for pathways of both fire alarm and emergency communications circuits in much more detail, including information on pathways using the Internet or broadband connections and survivability options. The old method of using styles of circuits has been replaced with an expanded list of classes to incorporate newer methods of signal transmission. It includes information for all types of circuits.

Information on fire safety control functions has been relocated to a new chapter, now called Emergency Control Functions and Interfaces (Chapter 21). This chapter didn’t add or change the requirements. Nonfire alarm users will need to interface with the fire alarm system, and this should make it easier to find the requirements.

Chapter 24, Emergency Communications Systems, has sections on both one- and two-way communications as well as separate sections on both in-building and wide-area (outdoor) emergency voice alarm and MNS. It also includes the survivability requirements for their circuits. It is important that circuits can survive a fire condition long enough to be effective. The one-way communications section includes audible emergency voice alarm systems, in-building MNS, visual communications (both strobes and textual visual notification), and wide-area mass notification.

Wide-area communications include information on high-power speaker arrays for outdoor areas and distributed- recipient MNS (e-mail, text messaging, etc.). For the first time, under certain circumstances, a signal other than fire alarm could have the highest priority. Locally generated MNS, based on a risk analysis, could override a fire alarm signal.

The two-way communications section includes wired firefighter telephone circuits, in-building radio systems, area of refuge communications and elevator communications.

There is an extensive section on performance-based design for emergency communications with goals, objectives, qualifications and performance criteria.

When using any type of voice system, occupants must be able to clearly understand the message, so they can react accordingly. In the past, the suggested test methods used the Speech Transmission Index method. This required the use of a meter for testing. The goal is to have a minimum of 0.7 common intelligibility score (CIS), so communications can be understood. Other methods now allow the use of the phonetically balanced word test, modified rhyme test, or Speech Intelligibility Index test. The 2010 NFPA 72 provides clearer guidelines for intelligibility testing. Annex D addresses speech intelligibility and is primarily based on NEMA Standard Publication SB 50-2008, “Emergency Communications Audio Intelligibility Applications Guide.” Visit for free access to this document.

Clearly, a lot of new information is available. Designers and installers should get familiar with the MNS and understand the properties of sound, as well. A lot of information on MNS is available today from manufacturers.

HAMMERBERG is currently the president/executive director of the Automatic Fire Alarm Association Inc. headquartered in Jasper, Ga. He serves on a number of NFPA committees, including the NFPA 72 Technical Correlating Committee and the Protected Premises Technical Committee. He can be reached at

About the Author

Thomas P. Hammerberg

Life Safety Columnist
Thomas P. Hammerberg, SET, CFPS is president of Hammerberg & Associates Inc. He serves as Director of Industry Relations for the Automatic Fire Alarm Association (AFAA) Inc. and represents the association on a number of NFPA committees, including the...

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