Which type of smoke detector uses a small amount of radioactive material to make the air within a sensing chamber conduct electricity?

Which type of smoke detector uses a small amount of radioactive material to make the air within a sensing chamber conduct electricity?

• A. Photoelectric Smoke Detector
• B. Carbon Monoxide Sensor
• C. Heat Detector
• D. Ionization Smoke Detector

Answer: (D)

Ionization smoke detectors rely on ionizing a small amount of air with radioactive material to create a conductive path between two electrodes. The radioactive source, typically americium-241, ionizes the air inside a sensing chamber, producing a steady current between the plates. When smoke particles enter the chamber, they attach to the ions, reducing the flow of charge and causing the current to fall below a threshold, which triggers the alarm. This is different from photoelectric detectors, which use a light beam and a sensor to detect smoke by light scattering, without any radiation involved. Other detectors (heat or carbon monoxide sensors) operate on entirely different principles and do not rely on ionizing radiation to detect smoke. The defining idea is the use of a sealed radioactive source to ionize air and create a detectable current that smoke interrupts.

Ionization smoke detectors rely on ionizing a small amount of air with radioactive material to create a conductive path between two electrodes. The radioactive source, typically americium-241, ionizes the air inside a sensing chamber, producing a steady current between the plates. When smoke particles enter the chamber, they attach to the ions, reducing the flow of charge and causing the current to fall below a threshold, which triggers the alarm. This is different from photoelectric detectors, which use a light beam and a sensor to detect smoke by light scattering, without any radiation involved. Other detectors (heat or carbon monoxide sensors) operate on entirely different principles and do not rely on ionizing radiation to detect smoke. The defining idea is the use of a sealed radioactive source to ionize air and create a detectable current that smoke interrupts.