Author(s): Wayne Moore. Published on July 1, 2015.

THE 2015 EDITION of NFPA 101®, Life Safety Code®, requires all new assembly occupancies with occupant loads of more than 300 and all theaters with more than one audience viewing room to have a fire alarm system. If the system consists of automatic detection, or if the building has protection from an automatic sprinkler system, then the design may eliminate all but one of the normally required manual fire alarm boxes.

Typically, the Life Safety Code requires that a person at the on-site alarm receiving station initiate occupant notification. This person may make these announcements over the paging system or, when such a system exists, over the in-building emergency voice/alarm communication systems (EVACS). Where the authority having jurisdiction determines that a constantly attended receiving station is impractical, then the Life Safety Code requires the owner to provide automatically transmitted evacuation or relocation instructions in accordance with NFPA 72®, National Fire Alarm and Signaling Code, and that a supervising station must monitor the fire alarm system in accordance with NFPA 72.

In the past, some designs used a non-voice evacuation system in addition to the public address system. Since the issuance of the 2010 edition of NFPA 72, the code has allowed the use of the public address system to provide occupant notification for fire and mass notification messaging. Thus, the building would not need any additional non-voice notification appliances. In fact, having horns sounding throughout the assembly seating space would likely interfere with the use of the public address system to inform the occupants of an emergency.

The system designer must first evaluate the PA system in order to use it for emergency messaging. The code requires the emergency communication system designer to provide evaluation attesting to the fact that the designer has evaluated the public address system and that it meets the performance requirements of Chapter 24 and the emergency response plan for the building.

When approved through the risk analysis process, the PA system must interface with the fire alarm system to deactivate the non-voice audible appliances to ensure the emergency messages will have priority and provide audible and intelligible communication throughout the space. However, the system need not provide this feature if the design uses only the PA system for all occupant notification.

Additionally, when the public address system includes individual or zone speaker volume controls, these controls must default to provide the proper emergency sound level when the design uses the public address system for an emergency mass notification or fire warning messages.

Of course, all of the intelligibility requirements for the voice systems apply regardless of whether the design uses the PA system or the EVACS for occupant notification. By allowing the interface of these two systems, NFPA 72 reduces the overall costs while maintaining operational effectiveness and reliability. Additionally, the 2016 edition of NFPA 72 now allows non-listed speakers to be used in acoustically challenging areas typically found in assembly occupancies.

Where required, designers must provide for the visible notification appliance network (i.e., strobes and textual signs). But designers should also understand that, if the occupant load exceeds 1,000 persons, the system must not provide visible signals in the seating area. In large assembly spaces such as these, the design must provide approved alternative visible notification, such as scoreboards, flat screens, message boards, or other electronic devices.

Because assembly occupancies present a number of fire and emergency messaging challenges, the designer must ensure that the required fire alarm systems and public address systems interface properly. The designer also must present a clear design narrative, so that the authority having jurisdiction may fully understand the interfaced operation prior to approving it. Meeting these challenges requires a strong background in the codes as well as a thorough knowledge of sound and communications principles.

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