For a room that is 54 ft by 54 ft, what minimum candela rating would be required for a single strobe to meet NFPA 72 requirements?

For a room that is 54 ft by 54 ft, what minimum candela rating would be required for a single strobe to meet NFPA 72 requirements?

• A. 75 cd
• B. 90 cd
• C. 110 cd
• D. 130 cd

Answer: (C)

Strobe visibility depends on how far the farthest occupant can be from the device and ensuring the strobe is bright enough to be seen under alarm conditions. NFPA 72 provides visibility requirements that scale with room size and the distance from the strobe to occupants. In a room that measures 54 by 54 feet, placing a single strobe on the ceiling (typical central mounting) means the farthest distance to an occupant is about 38 feet. At that distance, the code’s visibility table for a single strobe indicates a minimum candela rating of 110 cd to meet the required visibility. Lower ratings like 75 cd or 90 cd wouldn’t be bright enough at the farthest point, while 130 cd would be more than necessary for this room. So the minimum acceptable rating is 110 candela.

Strobe visibility depends on how far the farthest occupant can be from the device and ensuring the strobe is bright enough to be seen under alarm conditions. NFPA 72 provides visibility requirements that scale with room size and the distance from the strobe to occupants. In a room that measures 54 by 54 feet, placing a single strobe on the ceiling (typical central mounting) means the farthest distance to an occupant is about 38 feet. At that distance, the code’s visibility table for a single strobe indicates a minimum candela rating of 110 cd to meet the required visibility. Lower ratings like 75 cd or 90 cd wouldn’t be bright enough at the farthest point, while 130 cd would be more than necessary for this room. So the minimum acceptable rating is 110 candela.