Which device contains a small radioactive source used to ionize air inside a chamber and triggers an alarm when smoke shields the radiation?

• A. Ionization Detector
• B. Photoelectric Detector
• C. Heat Detector
• D. Flame Detector

Answer: (A)

An ionization detector uses a tiny radioactive source to ionize the air inside a small chamber, creating a steady current between two electrodes. When smoke enters, smoke particles attach to the ions, reducing the current. When the current falls below a set threshold, the alarm is triggered. This mechanism hinges on the radioactive source ionizing the air, which is why it’s the correct description. Other detectors rely on different principles—photoelectric detectors use a light beam and smoke scattering, heat detectors respond to high temperatures, and flame detectors sense flame radiation—none of which depend on a radioactive ionization process.