What type of alarm is activated by smaller invisible products of combustion?

Ionization alarms are specifically designed to detect smaller, invisible products of combustion, such as those produced by flaming fires. They use a small amount of radioactive material to ionize air within a sensing chamber, creating an electric current. When smoke enters the chamber, it disrupts the ionization process, triggering the alarm. This makes ionization alarms particularly effective for detecting fast-burning fires, where smoke particles are typically smaller and less dense.

In contrast, photoelectric alarms are more responsive to larger smoke particles that are produced in smoldering fires. Thermal alarms rely on temperature changes rather than smoke detection and activate when a certain heat threshold is met, which may not correlate with the presence of smoke or combustion products. Combination alarms include features of both ionization and photoelectric technologies, but they are not solely focused on the smaller, invisible particles that ionization alarms effectively detect.