Which devices are typically used as smoke detectors?

• A. Inconel loop
• B. Optical detectors
• C. Pneumatic systems
• D. Photoelectric cell devices

Answer: (D)

Smoke detection in aircraft commonly relies on optical, light-based sensors. A photoelectric detector uses a light source and a photodetector arranged so that normal air keeps the light path out of the detector. When smoke enters the sensing chamber, the smoke particles scatter or block the light and a signal is produced that triggers the alarm. This method is especially effective for detecting smoldering fires, which is why photoelectric cell devices are typically used as smoke detectors. Other options don’t describe a smoke-detection device: an inconel loop is not a smoke detector, pneumatic systems measure pressure, and while optical detectors cover the broad idea, the specific, standard smoke-detecting device described here is the photoelectric cell (optical) type.