Which best describes a false alarm?

A false alarm is typically understood as an event where an alarm system alerts on a condition that does not actually indicate a real threat or incident. In the context of this question, a scenario where an alarm is triggered due to a door not being shut properly illustrates a false alarm because it suggests an intrusion or problem that is not real — someone could simply have left the door ajar rather than indicating unauthorized entry or a true security breach.

This aligns with the concept of a false alarm where the conditions leading to the alert do not reflect an actual security threat. It emphasizes the issue of reliability in security systems and the potential for unnecessary responses to alarms that don’t reflect true incidents.

In contrast, other options tend to indicate situations that may involve genuine technical issues or environmental factors but do not fit the standard definition of a false alarm related to security issues. For instance, alarms activated during a power failure concern operational status rather than security; equipment malfunction denotes failure in the system rather than a misleading alert; and smoke detection certainly signals a real threat (presence of smoke) that is typically tied to fire risks.