In what scenario would all smoke alarms in a unit activate?

All smoke alarms in a unit activate when one smoke alarm detects smoke due to the interconnected nature of modern smoke alarm systems. When one alarm senses smoke, it triggers a signal that communicates with all other alarms in the system, leading to a simultaneous activation. This feature is essential for ensuring occupant safety, as it ensures that all residents are alerted to potential danger regardless of which part of the unit the smoke is detected in.

In contrast, other scenarios listed do not lead to simultaneous activation across all smoke alarms. For instance, when the power goes out, individual alarms may operate on battery backup, but they will not communicate or activate other alarms unless smoke is detected. Testing the system or using the test button typically results in a localized response from the alarm being tested, rather than triggering the entire network. Understanding this interconnected system is key for recognizing how modern safety equipment functions to enhance fire alert capabilities.