Last month served as an overview and introduction to mass notification systems (MNS) and emergency communications systems (ECS). As promised, we will now expand upon that material and discuss the various types of systems that fall under these headings.
The requirements for these systems are found within Chapter 24 of NFPA 72, National Fire Alarm and Signaling Code. As these systems may and do provide warning of more than a fire within a premises, the word “signaling” was recently added to the title of NFPA 72. First, we’ll examine system requirements and expectations, and then move on to define several specific types of systems.
Required or Not, Code Plays Role
A system may be either required or nonrequired, depending on its use and if it is required by a building or fire code or a governmental agency. At this time, there are no requirements for an ECS or MNS found within any of the model building or fire codes used within the United States.
However, there is one in the Occupational Safety & Health Administration (OSHA) requirements for Emergency Employee Alarm Systems, as found within Section 1910.165(a)(1) Part 1910 of Title 29, Labor, Code of Federal Regulations. These systems are intended to warn employees within a premise of an emergency other than a fire. The requirements have been in place for a number of years, prior to the U.S. Air Force requesting that the National Fire Protection Association (NFPA) promulgate a standard for MNS.
As with automatic fire alarm systems, a voluntary system still must be installed in accordance with Chapter 24. When a voluntary system is installed, the designer or installer must understand the needs and objectives of the building owner. The system must be able to meet their intended purpose. The wiring that is installed must also meet the requirements of NFPA 72 as well as NFPA 70, National Electrical Code. A voluntary system should not be installed in a nonapproved manner simply because the system itself it is not required.
Depending on the type of system to be installed, pathway survivability requirements found within Section 23.3.5 must be followed. Pathway survivability will ensure that the circuits for the system remain in operation for up to two hours. The levels of pathway survivability are found within Chapter 12 of NFPA 72, Circuits and Pathways. This is primarily to prevent the heat from a fire from taking out a circuit prior to alerting all of the occupants within a premise. As ECS and MNS will be used to provide instructions to the occupants over a period of time, or to provide communications for emergency personnel, it is vital these circuits stay in operation as long as possible.
For the first time within NFPA 72, a signal other than one from a fire detection device is now allowed to have priority over a fire alarm signal. This is outlined in Section 10.6, Signal Priority, found within Chapter 10, Fundamentals. For this to occur, a risk analysis shall be conducted in accordance with Section 126.96.36.199, Voice Message Priority. This should only be performed by someone competent in what is required for a risk analysis, such as a fire protection engineer. Note that the reference to paragraph 188.8.131.52 found in some printings of the 2010 edition of NFPA 72 is incorrect.
8 Different Types of Systems
There are two basic types of systems, one-way and two-way. Within the one-way classification, the following types are found:
In-Building Fire Emergency Voice/Alarm Communications Systems (EVACS) — This is the traditional voice alarm system that has been within NFPA 72 for a number of cycles. It allows for a prerecorded message to be broadcast over speakers, providing different messages, depending on where the event is, and the location of those within the building. It also allows for an “all call” or selected zone live paging from emergency responders. These systems are found in Section 24.4.1.
In-Building Mass Notification Systems — These systems are intended to alert occupants within a building of emergency events other than a fire, such as for security, weather, hazardous releases and so forth. They may also alert occupants of a fire. The coverage of these systems may be within an individual building, areas surrounding the building or other designated outdoor areas. While in some respects these systems may be similar to a 24.4.1 system, they do allow other means of alerting building occupants. The messages may be textual, such as found in signage. These systems may also be tied into wide-area notification systems, which are discussed next. These systems are found in Section 24.4.2
Wide-Area Mass Notification Systems — These systems are intended to provide real-time notification over a wide outdoor area. This may be seen as the older civil defense air raid sirens. These systems provide more than just a siren, however, as they now include voice messages. Within the U.S. military, these systems have been referred to as giant voice systems. They include high power speaker arrays (HPSA). These systems are found in Section 24.4.3.
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