The fire alarm system's back-up battery capacity must be able to monitor the premises for at least how many hours?

• A. 8 hours
• B. 12 hours
• C. 24 hours
• D. 48 hours

Answer: (C)

Standby power must keep the fire alarm system operating during a power outage, ensuring continuous monitoring and signaling for life-safety. The established requirement is that the backup battery capacity can power the system for at least 24 hours. This duration covers typical outage scenarios and gives time for power restoration or switch to an alternative source without losing notification or supervision. Eight or twelve hours would not provide sufficient coverage for longer outages, risking loss of monitoring or delayed response. Forty-eight hours would exceed the minimum standard and is not generally mandated for most occupancies, though larger or specially described systems might have different needs. In short, twenty-four hours is the standard minimum that ensures reliable operation through a common outage window.