Residential fire alarm systems must have a backup battery capable of operating for how many hours under normal conditions?

In residential fire alarm systems, having a backup battery is crucial for ensuring that the system continues to operate during a power outage. The standard requirement is for the backup battery to be capable of providing power for a minimum of 24 hours under normal conditions. This duration ensures that the alarm system remains functional long enough for residents to be alerted in the event of a fire, even if there is a prolonged power interruption.

A 24-hour backup power supply allows time for first responders to arrive and assists in safeguarding residents until a more stable power source can be restored. This specification aligns with NFPA (National Fire Protection Association) guidelines, which emphasize the importance of reliable operation of fire alarm systems to enhance occupant safety. Other options do not meet the requirements established for sufficient backup time to ensure the system's efficacy during emergencies.