What type of smoke detector uses radioactive isotopes?

The correct answer is the ionization chamber, which is a specific type of smoke detector that utilizes radioactive isotopes, typically Americium-241. In an ionization smoke detector, there are two charged plates separated by a small air gap. A small amount of ionizing radiation from the radioactive material ionizes the air particles in the chamber, allowing a small, constant current to flow between the plates.

When smoke enters the chamber, it disrupts this ionization process, effectively reducing the current flow. This change is detected by the smoke alarm circuitry, which then triggers the alarm to alert occupants of a potential fire.

Ionization smoke detectors are particularly effective at detecting fast, flaming fires that produce little visible smoke. They are often used in residential settings due to their sensitivity in those situations. In contrast, other types of smoke detectors, like photoelectric detectors, use a light source and sensor to detect smoke and are better suited for smoldering fires. The fixed temperature detector and combination detector utilize different mechanisms, making them distinct from the ionization chamber in terms of operational principles.