Which device is an initiating device?

• A. Duct smoke detector
• B. Water flow switch
• C. Tamper switch
• D. Strobe

Answer: (A)

Initiating devices start the fire alarm sequence by detecting a condition and signaling the control panel. A duct smoke detector fits this role because it continuously monitors the air in the duct for smoke and, when detected, sends an alarm signal to the panel to start the notification process. The other items serve different functions: a water flow switch is tied to the sprinkler system and may trigger an alarm in some setups, but it’s more tied to the suppression system; a tamper switch is supervisory, indicating a device has been opened or tampered with; and a strobe is a notification appliance that alerts occupants but does not initiate the alarm itself. So the duct smoke detector is the initiating device.