Communication Systems & Their Challenges
We have discussed different types of emergency communications systems and how they work.
Essentially, emergency communications systems are intended to protect life by notifying occupants of buildings of emergency situations and communicating the information necessary to facilitate appropriate responses and actions. These systems are also intended to communicate information about various emergencies including:
- Human-caused events that may be accidental or intentional
- Other dangerous situations
- Natural disasters
Chapter 24: Emergency Communications Systems (ECS) in NFPA 72 was only added to the Code in 2010. It covers the minimum requirements for installation, performance, and the reliability of communications systems without establishing specific methods by which these requirements should be met. As discussed, it also covers in-building fire emergency voice/alarm communication systems (EVACS) that are used for mass notification system design. This includes:
- Automatic response for recipients of signals that indicate a fire or other emergency
- Voice evacuation messages
- Positive alarm sequences
- Operating controls
- Loudspeakers and their enclosures, as well as loudspeaker circuits
- Tones, including those transmitted by some types of loudspeaker
- Requirements for relocation and partial evacuation
- Signal zoning for fire and smoke areas
- System operations that relate to personnel permitted to control message initiation over the mass notification system
- Notification coverage that provides for live voice and prerecorded localized messaging activated by the mass notification system
- Voice message priority that establishes the priority of mass notification systems
- Volume control that can be adjusted
- Visual notifications for those who are hearing impaired or for situations where there is a lot of noise, making it difficult for anyone to hear properly
- Public address (PA) systems that are used for emergency communications
- Public address (PA) systems that interface with facility fire alarm systems
Additionally, the Code deals with two-way radio communications enhancement systems that prevent interference and specify installation and design. Emergency command centers for emergency communications centers and emergency communications control units are also specified.
Supplement 2 of the 2010 National Fire Alarm and Signaling Code Handbook, Emergency Communications Systems Design and Application Challenges by Wayne D. Moore focuses on systems where mass notification system design includes the use of speakers. These systems often have the most design challenges including both in-building and wide-area MNS, EVAS, and two-way emergency services ECS, elevator ECS, and in areas of refuge ECS. Each of these is discussed in some detail.
Ultimately, the challenge is to ensure that the system designed will deliver intelligible messages in spite of issues like background noise, acoustical properties of materials used for the construction of the building, possible distortion related to the bandwidth of sound equipment, and even the voice/accent of the person delivering the message.
The answers to these challenges lie primarily in the mass notification system design. And, as you have seen, this goes well beyond the basic requirements of a general fire alarm voice evacuation system.