How voice systems can meet the notification challenges of the industrial sector
BY WAYNE D. MOORE
Industrial facilities present a variety of emergency communications challenges, including high noise levels and the presence of products either manufactured or stored on the premises that present significant fire or explosion hazards. The Occupational Safety and Health Administration requires industrial facilities to notify employees of all alarm conditions and references NFPA 72®, National Fire Alarm and Signaling Code, for employee notification requirements.
In many older industrial buildings, emergency warning systems used coded signals to indicate an emergency. The use of coded signals required training for employees to understand what each “code” meant and provided ineffective notification to visitors. To ensure a rapid and understandable notification of an emergency, voice communication became the obvious choice.
The current requirements contained in NFPA 72 permit an industrial facility to use in-building fire emergency voice/alarm communications systems (EVACS) for nonemergency mass notification, including routine paging. Specifically, NFPA 72 states that the priority of mass notification messages over fire alarm evacuation “shall be permitted when evaluated by the stakeholders” in accordance with the risk analysis section of the code. This can prove very cost effective, eliminating the need for separate communication systems within a facility. The design of the notification system must ensure the occupants can both hear and understand the voice messages, meaning that NFPA 72 requires the system designer to ensure both the audibility and intelligibility of the voice messages.
The code includes a requirement to “incorporate designation of acoustically distinguishable spaces (ADS) within the occupiable areas as required in Chapter 18.” This new concept has prompted additional guidance found in Annex A, which states: “In an ADS that is a non-acoustically challenging area, designing for audibility will typically result in an intelligible system provided minimum speaker guidelines are followed. Areas typically considered to be non-acoustically challenging include traditional office environments, hotel guest rooms, dwelling units, and spaces with carpeting and furnishings.”
Industrial facilities will typically have more acoustically challenging spaces than other occupancies. These spaces, with high ceilings and hard surfaces, require special attention in the design stage. In some cases, the conditions will warrant more speakers with lower power taps in order to help reduce the effect of reverberation and ensure intelligibility of the messages. Where a design cannot obtain the required intelligibility, the code permits occupants to move up to 30 feet in order to reach an area where they can hear an intelligible message.
In those areas where the ambient noise level exceeds 85 dB—roughly the noise level in a typical factory setting, according to the industry website industrialnoisecontrol.com—the code requires an alternate means of notification when the system cannot deliver an intelligible message. This alternate means could include visible notification appliances, such as strobes, or some form of a message board or video monitor. In general, though, designers should avoid using strobes for other than fire alarm notification, since strobes have become ingrained in all areas of society as indicators of fire and of the need for occupants to evacuate the building. However, when a design for a combination system uses strobes to indicate a general emergency, the strobes must have either no markings or should be stamped or imprinted with the marking “ALERT.”
The code permits the use of textual and graphical visible notification appliances for primary or supplemental notification. For example, a design that provides emergency mass notification information to the general public, or specific individuals, in high noise areas may use these appliances as a means of primary notification.