Which type of smoke alarm uses a sensor to detect ionization changes?

The correct answer is an ionization alarm. This type of smoke alarm utilizes a small amount of radioactive material that ionizes the air in a sensing chamber. When smoke enters this chamber, it disrupts the flow of ions, which in turn changes the current in the chamber. This change in ionization triggers the alarm to go off. Ionization alarms are particularly effective at detecting fast-flaming fires, which produce small particles that are more likely to enter the sensing chamber and disrupt the ionization process.

Understanding how ionization alarms work highlights their unique strengths in fire detection, particularly in scenarios involving flaming fires, while other types of smoke alarms, such as photoelectric alarms, operate based on different principles, focusing instead on light scattering to detect smoke from smoldering fires.