How long must secondary power supplies support a fire alarm system's alarm after standby?

Fire alarm systems are designed to ensure reliable operation during emergencies, which includes being able to sound alarms and support critical functions in the event of a power failure. The requirement for secondary power supplies to support an alarm after a standby period is crucial for the system's effectiveness.

The correct duration, which is 15 minutes, is established to allow sufficient time for the fire alarm system to continue functioning independently, even in the event of a primary power loss. This timeframe helps ensure that occupants have an adequate warning during an emergency situation, as well as allowing for the potential need to evacuate or respond to the threat, without relying solely on the primary power source.

In contrast, shorter durations would not provide enough time for critical functions during emergencies, while longer durations may result in increased costs or unnecessary complexity without additional safety benefits. It's essential that fire alarm systems are compliant with these standards to enhance the safety of building occupants in a fire event.