NFPA Journal

If so, you represent the vast majority of people that the NFPA 72®, National Fire Alarm and Signaling Code, Technical Committees think about when they make changes to the code. Their broad goal is to change the code in a fashion that makes installed fire alarm systems more operationally reliable, permits the proper use of the most modern technology, and incorporates features to keep the fire alarm systems free of false alarms.

The NFPA Standards Council placed the code on a three-year cycle in order to incorporate changes and updates as needed and in a timely fashion. These changes happen for a variety of reasons, including evolving technology, new research related to fire alarm systems, changes necessitated by the impact of specific fire losses, and fire alarm design and installation experience that is reported to the Technical Committees by manufacturers, installers, users, and authorities having jurisdiction.

The 2016 edition of NFPA 72 has many changes proposed, some technical and some editorial, and some will be addressed in certified amending motions at the NFPA Technical Meeting in Chicago. Three of the more important changes will have a major impact on the design and installation of fire alarm and mass notification systems (MNS). These changes include the design option to use a non-listed speaker in voice systems to meet the intelligibility performance required by the code where a listed fire alarm speaker will not perform as required; performance requirements and wiring requirements that will permit fire alarm and mass notification systems to use a computer network infrastructure; and more specific listing requirements of the 520 Hz low-frequency audible notification appliance requirements that became a required feature of all new fire alarm systems installed after January 1, 2014. All of these changes intend to permit the use of new technology to serve users and help ensure the satisfaction of the broad goals of a false-alarm-free and operationally reliable fire alarm system.

Meeting the intelligibility performance requirements

The first change of importance occurs in the emergency communications systems, or ECS, area of the code. One of the major “sea changes” that came into the code appeared in the 2010 edition as a new chapter for ECS, which said that a typical emergency communications system could consist of either an emergency voice/alarm communications system or a mass notification system.

In the first case, depending on the location of the detected fire, the fire alarm systems’ speakers produce messages that advise the occupants to either relocate to a safer part of the building or evacuate. In the second case, an MNS could provide additional messages that might include information regarding extreme weather, terrorist events, active shooters on the property, or a host of other emergency conditions that require specific response by the occupants of a building or group of buildings.

The speakers, amplifiers, and control equipment used as the components for these systems were required to include design features to ensure that the occupants receiving the messages produced and transmitted throughout the building could accurately interpret the content of the messages. For voice messages, this meant that the message must be intelligible to the listeners. The proliferation of these systems has brought the importance of voice intelligibility performance into sharper focus; the code requires that a national testing laboratory, such as Underwriters Laboratories (UL), must test and list to a specific standard every speaker used in a fire alarm system. These speakers must all meet the same frequency response and other performance requirements of the UL standard and generally prove sufficient for most applications.

However, based on performance requirements that first appeared in the 2010 edition of NFPA 72, ECS designers have discovered that the listed fire alarm speakers typically available cannot meet the intelligibility performance needed in acoustically challenging areas, such as atriums and other hard-surface environments with extended reverberation times. These acoustically challenging environments require special speakers designed to overcome the intelligibility problems of these spaces. Speaker manufacturers make speakers capable of providing intelligible information in such environments, but these speakers have neither received listing for use in fire alarm systems, nor do most sound and communications manufacturers see the need to seek such listing.

In response, the Technical Committee determined that intelligibility of the messages presented to the occupants made a more significant impact on the level of life safety provided by an ECS than a speaker’s listing status. As a result, the committee has now permitted the installation of non-listed loudspeakers in order to achieve the intelligibility for that specific notification zone serving an acoustically challenging environment. This choice allows fire alarm systems to use some of the same technological advances in speaker systems that other public address and audio distribution systems have used to overcome challenges to the intelligibility of signals.

Using Ethernet and network infrastructure

Another sea change occurring inside the 2016 edition of the code will allow the controlled use of the Ethernet and other computer networks in a building to interconnect the components of a fire alarm system.

Traditionally, the distributed components of a fire alarm system have connected with each other using a two-conductor cable. Such a cable interconnects all of the fire alarm initiating devices and fire alarm notification appliances to a fire alarm control panel. However, with the proliferation and availability of computer networks, we now live in an age where we “connect” to almost every communication device we use through the Ethernet or other computer networks.

Fire alarm systems have long used computer-based technology to connect various devices and appliances to the fire alarm system control unit. But fire alarm systems have always used a private, customized network particular to the specific fire alarm system control unit in order to ensure a suitably high level of integrity and to ensure that no other communications on that network would interfere with the operation of the fire alarm system. As the Annex of the code explains, in more technical language: “Ethernet devices are addressable but with an important distinction from device addresses on a traditional signaling line circuit (SLC) multi-drop loop. A device with an Ethernet address is, in most cases, a physical endpoint connected to a dedicated cable and distributed throughout a building using switches and routers. Traditional SLC devices are all wired on the same communication line (in parallel), similar to an old party-line telephone system. By comparison, Ethernet’s network switches direct each data packet to its intended recipient device like our modern phone systems.”

The fact remains that rigorous computer networks now exist in many buildings. This has prompted a question to the NFPA 72 Correlating Committee as to why building owners can’t utilize these same networks to connect all of the fire alarm system devices and appliances to a fire alarm control unit. Allowing the use of the existing computer network in a building would greatly reduce wiring costs, proponents argue, and provide greater flexibility for changes and additions that heretofore presented a costly and time-consuming endeavor.

Naturally, the Technical Committees had reservations about the use of these networks. By using a shared network, how would the fire alarm system maintain priority if other signal traffic overloaded the capability of the network? How would the fire alarm system monitor the integrity of the network, as it had done with its private network? An informal study conducted by a leading manufacturer that looked at fire alarm system status monitoring via the Ethernet revealed that Ethernet monitoring experiences “down time” or unavailability from 0.75 percent to 1.50 percent of the time. Most of the events that contribute to this down time arise when information technology personnel take other systems down for upgrades, reconfigurations, rerouting of cables, testing, and maintenance. It appeared to the Technical Committees evaluating the use of Ethernet networks that using such a network as a single means of fire alarm system device and appliance interconnection may present reliability issues.

In response to these concerns, the Technical Committees have developed a new circuit designation called “Class N.” They have defined this circuit as including two or more pathways that must have their operational capability verified through end-to-end communication. The redundant path intends to compensate for Ethernet wiring that cannot meet all of the fault monitoring requirements that normally apply to traditional wiring methods used for fire alarm circuits. The use of these computer networks as allowed by the code, along with the feedback from designers, authorities having jurisdiction, and installers will certainly make this topic one of ongoing interest.

520 Hz low frequency audible appliance requirements

As of January 1, 2014, all sleeping areas in new residential buildings were required by the code to have listed low-frequency (520 Hz) audible appliances provided to awaken occupants in the event of a fire. Research performed in Australia and supported by the Fire Protection Research Foundation showed that a low-frequency signal was more successful at awakening the very young and the elderly than a traditional higher-frequency (3,000 Hz) signal, a finding that had significant life safety ramifications for these groups.

Because the compliance date has now passed, the 2016 edition of NFPA 72 will simply state the requirements and will require that a nationally recognized testing laboratory test and list the appliances producing the low-frequency tone. To comply with these requirements and produce the necessary signal, the code permits the use of either a listed stand-alone appliance or the use of a listed fire alarm system consisting of a recorded low-frequency signal delivered through an amplifier and loudspeaker. An emergency communications system would more likely use this latter method to produce the required signal.

It is interesting that the three important changes addressed here—the use of nonlisted fire alarm speakers, utilizing existing computer networks to connect fire alarm systems, and the requirement of 520 Hz audible appliances in sleeping areas—have the potential to directly affect the life safety of those protected by fire alarm systems. In addition, the broadening of the use of Ethernet and other computer networks has the potential to greatly lower costs of both initial fire alarm system installation, and later upgrades or renovations to such systems.

The importance of each of these changes, coupled with other changes made throughout the code, meet the Technical Committees’ goals of improving overall fire alarm system reliability. Ultimately, a host of factors is responsible for changes to the code, and as the Technical Committees look to develop those changes for the 2019 edition of the National Fire Alarm and Signaling Code, they will surely make further attempts to develop false-alarm-free fire alarm systems so that when the alarm sounds in your building, you will not hesitate to leave.

WAYNE MOORE, P.E., FSFPE, is vice president at JENSEN HUGHES.