In a cross-zoned smoke detection system, what must happen after a detector is activated and before the alarm sounds?

• A. A second detector must activate.
• B. A sprinkler head must also be activated.
• C. The detector must continue reverting to alarm after three attempts at auto-reset.
• D. A human must manually activate the alarm.

Answer: (A)

In cross-zoning, the system uses two independent detectors in different zones to confirm a real fire before sounding the alarm. After one detector senses smoke, the alarm isn’t triggered yet; the system waits for a second detector in another zone to also indicate smoke. This cross-verification helps prevent false alarms from a single detector or local dust, vibration, or fault. Once a second detector in a different zone confirms the event, the alarm sounds.

Sprinkler activation isn’t part of the detector-confirmation process, auto-reset attempts aren’t what initiate the alarm, and manual activation isn’t required in this automatic cross-zoned setup.