Ionized smoke detectors utilize what material for smoke detection?

Ionized smoke detectors specifically use radioactive material, typically americium-241, to detect smoke. This type of detector operates based on the principle of ionization, where the radioactive material emits alpha particles that ionize the air within the sensing chamber. In a smoke-free environment, the ionization creates a conductive path allowing a small current to flow.

When smoke enters the chamber, it disrupts this ionization process by attaching to the ions, reducing the number of charged particles available to carry the current. This change in current triggers the alarm.

The use of radioactive material is key to the functionality of ionized smoke detectors, making them highly effective in detecting fast-burning fires. Other materials listed, such as carbon dioxide, flammable gas, or chemical sensors, do not play a role in the ionization process or in the smoke detection mechanism of these specific detectors.