Fire Alarm Strobe mounting height requirement

Questions about Georgia Codes and Standards

Fire Alarm Strobe mounting height requirement

Postby Blackstone on Thu Nov 20, 2008 11:02 pm

Notification Appliances

The U.S. Architectural and Transportation Barriers Compliance Board’s Bulletin #2: Visual Alarms, indicates that photometric calculations of lamp intensity for mounting heights of 80-inches and of 96-inches show only nominal differences and can be practically considered to be equivalent. Based upon this bulletin, wall mounted visual notification appliances located at least 80-inches from the finish floor of the notification area to the bottom of the strobe lens (or 6-inches below the ceiling – whichever is lower), but no higher than 96-inches, is accepted as complying with the requirements of 120-3-20-.39(3)(f) as an equivalent facilitation per 120-3-20-.04(2). This mounting range is also in compliance with NFPA 72 (1996), Section 6-4.4 requirements.

The maximum mounting height for wall mounted appliances is limited to no higher than 96-inches as the illumination from these visible appliances is reduce by distance (inverse square law) which becomes drastically reduced with the angle from a horizontal plane through the appliance. Devices requiring mounting heights greater than 96-inches due to high shelving or other obstructions may qualify for the use of ceiling mounted notification appliances. 120-3-20-.39(3)(g) recognizes ceiling mounted notification devices for large spaces as wall mounted appliances are unable to reach the center of these spaces. Typically ceiling mounted notification appliances are acceptable as an equivalent facilitation only where wall mounted devices are undesirable due to obstructions or damage, or where they provide better performance. Similar to wall mounted devices, illumination from these ceiling mounted visible appliances is reduce by distance (inverse square law) which becomes drastically reduced with the angle from a vertical plane through the appliance, however this reduction has been addressed and tabulated by UL 1971 in a vertical dispersion table for ceiling mounted notification devices that can be used in photometric calculations.
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