In a cross zoned smoke detection system, what must occur before the alarm sounds?

• A. A second detection device must activate
• B. The first detector must be cleaned
• C. The fire must be visible
• D. The system must be reset

Answer: (A)

In cross zoning, the alarm only sounds after corroboration from a second detector in a different area. This design prevents false alarms by requiring two independent detectors to indicate smoke before the system trips. So the key idea is that a second detection device must activate to trigger the audible alarm. Maintenance actions like cleaning the first detector aren’t what set off the alarm, and the fire doesn’t need to be visibly burning for the system to respond. Resetting the system isn't what initiates the alarm; it’s what you do after an alarm to restore normal operation.