If primary power fails on a fire alarm system, which of the following is required?

If primary power fails on a fire alarm system, which of the following is required?

• A. No signals shall be lost or delayed by more than 5 seconds
• B. No signals shall be lost or delayed by more than 10 seconds
• C. All signals shall be transmitted instantly
• D. Signals may be delayed up to 20 seconds

Answer: (B)

When primary power fails, the fire alarm system must continue operating on its backup power while still delivering signals in a timely way. The standard sets a practical limit on how long signaling can be delayed to ensure that alarms reach the monitoring center or annunciation points without leaving gaps in notification. That limit is ten seconds, so no signals should be lost or delayed beyond that window. A tighter five-second limit would be more stringent than required in this scenario, and insisting on instant transmission isn’t realistic given the switch to backup power and the signaling path. Allowing delays up to twenty seconds would compromise safety by slowing down notification and response.

When primary power fails, the fire alarm system must continue operating on its backup power while still delivering signals in a timely way. The standard sets a practical limit on how long signaling can be delayed to ensure that alarms reach the monitoring center or annunciation points without leaving gaps in notification. That limit is ten seconds, so no signals should be lost or delayed beyond that window.

A tighter five-second limit would be more stringent than required in this scenario, and insisting on instant transmission isn’t realistic given the switch to backup power and the signaling path. Allowing delays up to twenty seconds would compromise safety by slowing down notification and response.