NFPA Journal - July/August 2012 - (Page 40)
ALARM + DETECTION SYSTEMS
wayne d. moore, p.e., fsfpe
May I Have Your Attention, Please?
Evaluating the effectiveness of PA systems for emergency communications
n the “New Assembly” section of the 2012 edition of NFPA 101®, Life Safety Code®, Paragraph 22.214.171.124.1 requires that assembly occupancies with occupant loads of more than 300 and all theaters with more than one audience viewing room have an approved fire alarm system. The code also requires that occupants be notified from a constantly attended receiving station via a voice communi-
NFPA 72 Now requires the PA system designer to evaluate the proposed system to determine applicability and compliance. cation or a public address (PA) system, as long as it meets the following conditions: “(1) Occupant notification, either live or recorded, shall be initiated at a constantly attended receiving station by personnel trained to respond to an emergency. (2) An approved secondary power supply shall be provided for other than existing, previously approved systems. (3) The system shall be audible above the expected ambient noise level. (4) Emergency announcements shall take precedence over any other use.” Annex A of the Life Safety Code offers an alternative to the requirements of NFPA 72®, National Fire Alarm and Signaling Code, because in some large venues the typical fire alarm system may not prove effective in notifying the occupants due to a facility’s physical configuration or the noise level the system must overcome to deliver an intelligible message. In most instances, the PA system designed for a building, whether
a large assembly occupancy or a large mercantile mall, will deliver an intelligible message throughout the occupied spaces. However, that may not be true for the smaller venues permitted to use the PA system for occupant notification. And until the 2010 edition, NFPA 72 offered no guidance or requirements for using a PA system for emergency voice notification. According to the 2010 edition of NFPA 72, when an owner chooses to use a PA system for emergency communications, the system designer is required to evaluate the proposed system to determine applicability and compliance. The code also requires the designer to sign a document attesting to the fact that he or she has evaluated the system and deemed it reliable and able to provide emergency communications for the facility because it meets the requirements determined by Chapter 24 of the 2010 edition of NFPA 72 and by a risk analysis. The document should be kept with the fire alarm record drawings. When the PA system interfaces with the building fire alarm system and delivers both emergency fire evacuation messages and mass notification messages, it must meet specific code requirements. First, the PA system must provide, either internally as a design feature or with an approved or listed external controller, a signal to control the building’s fire alarm system for the purpose of deactivating the fire alarm’s audible and visible
wayne d. moore, p.e., fsfpe, is a principal with Hughes Associates.
NFPA JOURNAL JULY/AUGUST 2012
Illustration: Richard A. Goldberg
notification appliances in accordance with NFPA 72 requirements. The PA system must also have all the following features to be considered code-compliant: “(1) Emergency messages must have priority over nonemergency messages. (2) All individual or zone speaker volume controls must default to the emergency sound level when used for an emergency mass notification message. (3) When monitoring of circuit integrity is provided by the public address system, monitoring must continue, even if local speaker volume controls are placed in the ‘off’ position. (4) The required visible notification appliance network (i.e., strobes and textual signs) must be provided where required.” The 2010 edition of NFPA 72 addresses the concerns that a PA system may not provide the required emergency service. Regardless of the venue size, fire officials now have requirements and guidelines by which to judge the system’s effectiveness.
Table of Contents for the Digital Edition of NFPA Journal - July/August 2012
NFPA Journal - July/august 2012
In a Flash
Fenway at 100
Safety at Center Stage
Firefighter Fatalities in the United States, 2011
NFPA Journal - July/August 2012