Learn the Code: NFPA 72
Jan 23, 2012 2:24 PM
Mass Notification Supplement
InfoComm’s white paper on the 2010 Edition of NFPA 72 is probably the best introductory resource out there. It combs through documentation that is largely unfamiliar to our industry and gleans some of the most important points (as well as some quite fascinating history)—before you read the code (and you should), read the whitepaper.
The 2010 edition of the National Fire ProtectionCode (NFPA 72)—which will roll out over the coming years—has been called the most significant revision of the National Fire Alarm Code since its creation. Specific to our industry is an emphasis on design, installation, and performance characteristics of audio and video components and systems. This is the first time that AV expertise has been explicitly been linked to life-safety and construction industries. This is in part because NFPA 72 also explicitly deals with what experience has taught us—that emergencies and threats to life safety go far beyond fires and many require more sophisticated warning systems and communication.
While the adoption of NFPA 72 is in its very early stages, publicity surrounding it has already created opportunity, as customers anticipate compliance with the code or are motivated by it to simply build better emergency notification systems. Many AV professionals are already familiar with the National Electrical Code, also known as NFPA 70. It provides minimum standards and guidelines for the installation of electrical conductors, equipment, and raceways; signaling and communications conductors, equipment, and raceways; and optical fiber cables and raceways. Today, NFPA 70 is used throughout the world.
NFPA 72 will also one day exert similar influence standard design and specifications. In its current form it covers the application, installation, location, performance, inspection, testing and maintenance of fire alarm systems, supervising station alarm systems, public emergency alarm reporting systems, fire warning equipment and ECS, along with their components. Its purpose is to establish minimum required levels of performance, but not the only methods by which these requirements are to be achieved. However, if adopted by a local authority having jurisdiction (AHJ), NFPA 72 requirements must be met or surpassed in order to pass inspection and acquire certificates of occupancy.
Here is a brief overview of what is covered in the InfoComm whitepaper: Of all the new content in the 2010 revision of NFPA 72, the two most relevant sections for AV professionals are Chapter 24, “Emergency Communications Systems,” and Annex D, “Speech Intelligibility”. These sections cover the important concepts of “minimum required levels” and the fact that the code allows for a variety of methods for satisfying the requirements.
Chapter 24 includes specific information about how an ECS must be designed and requires a risk analysis intended to anticipate and define the circumstances under which a mass notification signal “shall” have the ability to override the fire alarm evacuation signals, in order to redirect building occupants based on the condition or event. This is important because, for the first time, the code implies that auditory and visual signaling—and the systems that convey them—should be considered a high priority.
This section of the white paper further discusses the two classifications of emergency communications systems as defined in Chapter 24: one-way and two- way, and the variations on these systems. Chapter 24 covers wide-area mass notification systems, referring to systems for outdoor areas, including campus-wide voice systems, military base public address systems, civil defense warning systems, and large outdoor visible displays; this section covers the requirements for high-power speaker arrays.
Key components of Chapter 24 are the definitions and requirements for speech intelligibility. However, a precise and quantifiable definition of voice intelligibility is missing from the body of the code. Suggestions for what makes an intelligible ECS are included in Annex D, which is also required reading for AV professionals working on ECS installations. Just to give an idea of the kind of specifications NFPA 72 includes, consider this statement in Annex D: “the intelligibility of an emergency communication system is considered acceptable if at least 90 percent of the measurement locations within each ADS4 [acoustically distinguishable space] have a measured [Speech Transmission Index] of not less than 0.45 (0.65 CIS) and an average STI of not less than 0.50 STI (0.70 CIS).”
So in other words: less than perfect intelligibility and barely acceptable for a non-emergency sound system.
It is important to also consider the context of these new code requirements and the legal, business, and competitive implications. Aspects of the code clearly indicate a need for AV expertise and would seem to legitimize our place at the table with the other building trades.
Further, just as the code legitimizes AV expertise, the InfoComm paper astutely points out that those who study the code will recognize that it is still missing information about the auditory and visual communications experience—this is particularly true when it comes to video and digital signage. But even in the case of audio intelligibility there is virtually no discussion of acoustics.
As a result, InfoComm members are continuing to participate in the ongoing development of the code, as well as developing ANSI standards that will help clarify NFPA 72 requirements. The white paper discusses these efforts to clarify enclosed space acoustics, EQ optimization, dealing with unwanted sound, reproduced speech and music quality, and sound pressure level optimization.