Potter Fire Alarm Systems - Manual (Page 28)

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Fire Alarm Training • 8700055 • Rev F • 4/10
Where required, visual devices must be installed in the corridors of a building for visual notification. The corridor must be less
than 20 feet wide. If the corridor is wider than 20 feet then the requirements for the room spacing must be applied. The minimum
candela rating for the visual devices mounted in corridors is 15 cd. The strobes must be mounted within 15 feet of the end of the
corridor and cannot be spaced more than 100 feet apart on center. The visual devices may be mounted either on the wall or the
ceiling. They must be mounted in accordance with NFPA 72 for the proper height and placement. In addition, if there are any
interruptions in the corridor such as fire doors, partitions or changes in elevation the areas are to be viewed as separate areas.
An installer must be concerned with how visual devices, strobes in particular, are installed with respect to how many strobes are
in a field of view or room when activated. When more than two strobes are in the field of vision the strobes must be synchronized
to flash at the same time. Some people are prone to photosensitive epileptic seizures when exposed to random flashing lights and
synchronization of flashes prevent the seizure.
Room Spacing for Wall Mounted Visible Appliances (per NFPA 72)
Minimum Required Light Output (Effective Intensity, cd)
Max Room Size
ft.
One Light per Room
cd
Two Lights per Room
(Located on Opposite Walls)
Four Lights per Room
(One Light per Wall)
20 x 20 15 NA NA
28 x 28 30 Unknown Unknown
30 x 30 34 15 NA
40 x 40 60 30 15
45 x 45 75 Unknown Unknown
50 x 50 94 60 30
54 x 54 110 Unknown Unknown
60 x 60 135 95 30
70 x 70 184 95 60
80 x 80 240 135 60
90 x 90 304 185 95
100 x 100 375 240 95
110 x 110 455 240 135
120 x 120 540 305 135
130 x 130 635 375 185
NA = Not Allowable