Loud and Clear

Close attention needs to be paid if emergency communication and notification systems are to make themselves heard when it really counts. By Lee Richardson, National Fire Protection Association (NFPA)

Infrastructure requirements for emergency communication and notification systems are beginning to evolve to a higher level than ever before. The need for these systems is typically established through the mandates of federal, state or local jurisdictions and in some cases by adoption of the requirements of building or occupancy codes. Once the higher level need for the system and its basic features have been established, more detailed requirements for implementation are usually prescribed by referencing specific equipment/system installation standards. One such document is NFPA's 2010 edition of NFPA 72, National Fire Alarm and Signaling Code, which includes expanded coverage of emergency communications systems. The requirements of NFPA 72 are not occupancy specific and apply equally whether the installation of a system is required by mandate or required to meet the building or property owner's needs.

The emergency communication systems addressed by NFPA 72 include the traditional emergency voice/alarm communications systems and two-way telephone systems historically used in buildings for fire emergencies. However, the 2010 edition also includes new installation, performance and testing requirements for in-building mass notification systems, wide-area mass notification systems, and distributed recipient mass notification systems. Emergency communications systems for areas of refuge and two-way radio communications enhancement systems are also addressed in the 2010 edition.

Within the context of NFPA 72, mass notification systems are used to provide information and instructions to people in buildings, outdoor campus areas, or to selected individuals or groups of individuals in various locations in response to broad variety of emergency situations. These situations can include terrorist threats, weather emergencies, or biological, chemical or nuclear emergencies. Within buildings the infrastructure for these systems can be similar to that used in a more traditional fire alarm system. In fact the use of integrated systems to perform multiple functions has many operational and economic advantages and the requirements of the 2010 edition embrace this approach.

Earlier editions of the Code required fire alarm signals to take precedence over any other signal. The Code now recognizes that in some situations other signals may need to have a higher priority. To establish these priorities, designers of mass notification systems are required to perform a risk analysis that considers all the anticipated events that the system is expected to address. When identified by the risk analysis and the emergency response plan, signals and messages from non-fire emergencies are permitted to take priority over fire alarms signals and messages.

In addition to the requirements addressing signal and message priority, the Code includes more detailed requirements for fire alarm and mass notification system interface and coordination. Specific requirements are included for in-building mass notification systems when they interface fire alarm systems, building controls or wide area mass notification systems. A new section is provided in the Code on information, command and control, including requirements for a central control station and for emergency communications control units.

The expanded requirements provided for these systems also include visible notification appliances (strobes) and textual visible notification appliances (message displays). New requirements addressing strobe marking and lens color are provided along with a new subsection on text displays. Text display height above the floor, minimum character size, viewing distance and color are all addressed in detail.

New requirements and guidance are also provided for wide area (outdoor) mass notification systems. These provisions address access control (based on risk analysis), interface with other systems, protection of communication links, and detailed provisions for high power speaker arrays. Provisions for the latter address environmental conditions, power supply capacity, voice intelligibility, and tone audibility as well as considerations to prevent hearing damage.

The 2010 edition of NFPA 72 also includes new requirements to address two-way radio communications enhancement systems. Emergency response personnel often rely on portable radios for communication during an emergency. However communication inside buildings can be adversely affected by the building structure causing signal attenuation and/or interference. Radio communication enhancement systems such as bi-directional antennas and signal amplifiers are intended to ensure that radio coverage is provided throughout the building especially in critical areas. Extensive requirements are provided for the design, commissioning and testing of these systems. These address compatibility with public safety radio systems, radio frequencies, radio coverage, inbound and outbound signal strength, signal level testing, and system monitoring and annual testing.

New requirements are also provided in the Code for emergency communication systems for areas of rescue assistance used within buildings for individuals who are unable to use stairs during emergency evacuation. These systems provide two-way communication between remote refuge stations and a central control point.

One of the more important provisions for emergency communications systems is that they be able to reproduce voice messages so that the message is capable of being understood. If emergency information and instructions are not understandable by the occupants, the messages are of little value. While this may seem obvious and straightforward, in practice it can often be a real challenge. Intelligibility can be greatly affected by background noise and by reverberation due to hard surfaces in the area of installation. The proper distribution (number and location) of speakers and the sound level of the speakers both play are role in the design of these systems.

The 2010 edition of the Code includes updated requirements for the design, installation and testing of voice message systems to ensure they produce intelligible messages. The Code requires designers of these to designate acoustically distinguishable spaces (ADS) and whether or not they will require voice intelligibility. An ADS is defined by its physical boundary or by its acoustic or environmental characteristics. Some spaces may not require the voice messages to be intelligible, depending on the emergency response plan for the building. Intelligibility may not be achievable in other spaces due to very high ambient noise levels. In the latter cases, other notification arrangements may need to be provided and addressed in the emergency response plan. A new annex on speech intelligibility is included in the 2010 edition and provides extensive guidance for the design and especially the testing of voice communications systems.

While need for requirements for mass notification systems where originally promoted for application in US Department of Defense buildings throughout the world, they are certainly applicable to any number of commercial, industrial, and government applications where there is a need to inform or instruct people in an emergency. Versions of these systems have already been installed at some colleges and universities in response to recent campus violence. The 2010 edition of NFPA 72 provides a foundation of requirements to ensure these systems are installed and perform reliably and continue to do so.

A major component in the successful implementation of these systems cannot be taken lightly - need for careful assessment and planning prior to and during the system design. The potential scenarios that these systems can be called upon to address need to be carefully thought through and documented in emergency response plans and procedures. The development of messaging strategies and command and control strategies will be essential if these systems are to be used effectively. Further steps will also be needed to provide proper communication and interaction with various responsible authorities.

Lee Richardson is Senior Electrical Engineer and Staff Liaison for NFPA 72 at the National Fire Protection Association. For more information on this and other NFPA codes, visit www.nfpa.org.