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Author(s): Wayne Moore. Published on July 1, 2017.

The challenges of retrofitting voice evacuation in high-capacity assembly spaces

BY WAYNE D. MOORE

Retrofitting a fire alarm system in any occupancy can be challenging. But designing and installing new systems for renovated high-capacity assembly occupancies such as airports, entertainment venues, and convention facilities can be especially difficult.

Typically, the biggest mistake designers and contractors make comes from assuming the detection coverage and the type of fire alarm system required remain the same as when the building was constructed. This assumption can lead designers to believe that a simple one-for-one replacement of all initiating devices, notification appliances, and controls is sufficient. Nothing could be further from the truth.

While the requirements to connect the automatic sprinkler system to the fire alarm system to provide occupant notification will generally remain the same, the latest edition of NFPA 72®, National Fire Alarm and Signaling Code, offers new allowances for the in-building fire emergency voice/alarm communications systems (EVACS) and public address systems.

The code now permits the use of an emergency voice/alarm communications system as the public address system. Another option permits interfacing the public address system with the EVACS to use the PA speakers for both public address and fire alarm notification. This option includes specific requirements for the public address system operational controls and standby power. The obvious benefit is a reduction in costs that can result by using the same speakers throughout the building for public address and fire alarm notification. The installers must locate both the EVACS and the public address system controls in a constantly attended alarm receiving station.

The 2015 edition of NFPA 101®, Life Safety Code®, requires that occupant notification consist of voice announcements initiated by the person in the constantly attended receiving station. NFPA 101 permits the delivery of these announcements by either a voice communication or public address system, either of which may use automatically recorded or live voice announcements provided the initiation comes from the constantly attended receiving station by personnel trained to respond to an emergency. In certain cases, the authority having jurisdiction may determine that it would be impractical to provide a constantly attended receiving station. In this case, the system may use automatically transmitted evacuation or relocation instructions and, in accordance with NFPA 72, a supervising station must monitor the system.

Of course, both NFPA 72 and NFPA 101 require that emergency announcements take precedence over any other use. NFPA 101 requires that the audibility of the notification announcements must exceed the expected ambient noise level. NFPA 72 also addresses audibility, but permits the automatic reduction of the ambient noise level upon the receipt of an alarm. The designer will discover that NFPA 72 has new requirements for intelligibility that may not have existed at the time of the initial construction of the building.

The codes do not require visible signals in the assembly seating area, or the floor area used for any contest, performance, or entertainment. However, in high-capacity assembly areas such as airports, notification must be provided by alternative visible means such as scoreboards, message boards, flat screens, and other electronic devices.

When such buildings require a smoke control system actuated by smoke detection, stakeholders must take special care. Generally speaking, high-capacity assembly areas will have higher ceilings than normal. Designers should review the ceiling heights of each space and avoid placing spot-type smoke detectors on high ceilings. In these cases, designers should provide a more thorough review of the detection goals for any smoke detector used.

The widely held belief is that any smoke detector can provide early warning in these types of spaces—but that isn’t necessarily true. Designers must consider ceiling height and configuration and all other influences, such as air flow and expected fire size, that affect smoke movement and thus detection. Be aware of the challenges in this special occupancy and your designs will likely prove more reliable.

WAYNE D. MOORE is vice president at Jensen Hughes. Top Photograph: iStockPhotos