How can the operation of a photoelectric smoke detector be tested?

• A. Disconnecting power and inspecting the unit
• B. Exposing the detector to direct flame
• C. Actuating a test switch
• D. Covering the detector with a cloth

Answer: (C)

Testing a photoelectric smoke detector relies on using its built-in test feature to verify the unit’s ability to sense and alert. When you actuate the test switch, the detector runs its self-test routine and triggers its alarm, confirming that the sensing electronics, the audible alert, and any cockpit or cabin annunciators are all functioning together. This provides a safe, approved way to confirm the complete warning system is operable without introducing real smoke or flames.

Why this is the best approach: the test switch exercises the detector’s electronic alarm path and the associated annunciation, giving a reliable indication that the device and its interconnections are healthy. It verifies the system as a whole in a controlled, repeatable way, which is the goal of routine testing.

Why the other methods aren’t appropriate: disconnecting power and inspecting the unit doesn’t verify that the sensing element and alarm circuit will operate when needed; it’s only a static check and could leave the system untested in service. Exposing the detector to direct flame is dangerous, can compromise the unit, and is not an approved maintenance procedure. Covering the detector with a cloth may simulate obstructed sensing in a moment, but it does not reliably test the alarm system and can create unsafe conditions or damage if the cover shifts.