Mass Notification System Design
Mass notification systems (MNS) are used to provide people in buildings and other spaces with information and instructions when there is an emergency of some sort. They are designed to utilize various emergency communications systems including intelligible voice communications and visual signals. MNS include in-building fire emergency communications that incorporate voice and alarm systems as well as in-building and wide-area mass notification systems. These are all discussed in more detail later on.
Mass notification systems were originally set up as military solutions, but are now part and parcel of emergency communications systems.
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Control Units for MNS
Control units are system components that monitor inputs and control outputs though different types of circuits. These include emergency communications control units (ECCU) that can send mass notification messages to individuals buildings as well as zones of buildings, individual outdoor loudspeakers or zones of loudspeaker arrays, or outside areas, a single building, multiple buildings, or a combination of these.
Autonomous control units (ACU) are primary control units that are an essential part of in-building mass notification systems.
Additionally, there are fire alarm control units (FACU) and wireless control units that transmit, receive, and process wireless signals.
FACUs are important components of fire alarm systems and they are fundamental to mass notification system design. Provided with both primary and secondary power sources, FACUs receive signals from initiating devices that originate transmit of a change-of-state condition, for instance, a manual fire alarm box, a smoke detector, or a supervisory switch. They might also receive signals from other FACUs. The unit is designed to process these signals to determine required output functions.
There are four FACUs that are specified and therefore regulated by the National Fire Protection Association (NFPA) National Fire Alarm and Signaling Code NFPA 72.
- Master fire alarm control units that serve physical locations protected by fire alarm systems (known as protected premises),or a portion of protected premises, and accepts inputs from other FACUs.
- Protected premises (local) control units that simply serve part or all of protected premises.
- Dedicated function fire alarm control units that are also designed for protected premises but specifically to operate certain identified emergency control functions.
- Releasing service fire alarm control units that are protected premises units designed to release service that is part of a fire suppression system. These units are also designed to provide control outputs that manually or automatically release a fire suppression agent.
Emergency Communications Systems
Emergency communications systems are designed to warn people of emergency situations and communicate information that is needed to facilitate an appropriate response and action and in this way protect life and property.
NFPA 72 specifies six emergency communications systems but acknowledges that often a combination of systems are served via a single control system or through the interconnection of several systems. These commonly include fire alarms, mass notification systems, elevator communications, areas of refuge communications, and firefighter communications.
Individually defined systems are:
- One-way emergency communications systems that are designed to broadcast information in an emergency to people in one or more specified areas, either indoors or outdoors.
- Distributed recipient mass notification system (DRMNS) that are designed to communicate directly to targeted people and groups that are not necessarily in a contiguous area.
- In-building fire emergency voice/alarm communications systems that comprise dedicated automatic or manual equipment that is designed to originate and distribute voice instructions. When there is a fire, these systems also send alert and evacuation signals to the occupants of the building. This might include a warning to occupants of the presence of lethal carbon monoxide.
- In-building mass notification systems that send instructions and provide people in the building or group of buildings with information using intelligible voice communications in conjunction with visual signals that may be text, graphics, or tactile, or use other communication methods.
- Wide-area mass notification systems that are usually installed to service outdoor areas and provide real-time information to people who are in these areas. They may be designed to communicate with other notification systems, for instance, those that are provided for municipalities, military bases, campuses, or similar contiguous areas.
- Two-way emergency communications systems that comprise two categories:
- Systems that are intended to be used by occupants of the building
- Systems that will be used by firefighters, other emergency services personnel, and the police.
It stands to reason, therefore, that this type of emergency communication system is used to both communicate and exchange information including instructions, conditions of the local environment, the condition of people (including those in areas of refuge), acknowledgment of messages received, and importantly, to assure everyone that help is on the way.
When engineers design fire alarm systems, we identify certain zones which are defined areas within protected premises. These may be areas from which signals can be received, areas where signals can be sent, or areas where a specified form of control can be executed.
Notification zones are defined areas inside or outside buildings where people congregate to receive common notifications.
Sometimes fire alarm systems are used to assist with partial evacuation and relocation of occupants in an affected building. When this is a requirement it is essential that the system is designed and installed so that fire within a notification zone will not impair the control and operation of notification appliances that are located outside the notification zone.
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