How long must a secondary power source for household alarms function during an alarm?

The requirement for a secondary power source for household fire alarm systems to function for a minimum of 4 minutes during an alarm is based on safety standards established to ensure that alarms remain operational in the event of a primary power failure. This duration is critical because it allows enough time for the alarm systems to alert occupants to evacuate the premises safely during an emergency, even when the main power source is not available.

A secondary power source, often in the form of batteries, must be reliable and robust enough to sustain operations for this duration. The 4-minute standard strikes a balance between ensuring adequate alerting time while also being practical in terms of the battery life and maintenance requirements of the alarm system. This standard also reflects the recognition that alarms need to function effectively to protect lives and property without being overly burdensome in terms of equipment requirements.