What do ionization smoke detectors monitor in the air?

Ionization smoke detectors work by utilizing a small amount of radioactive material to create a constant flow of ions within a sensing chamber. In this environment, the ions are charged particles that facilitate the flow of an electrical current. When smoke enters this chamber, it disrupts the flow of ions by attaching to the charged particles, thereby reducing the current. This reduction in current is detected by the device and triggers the alarm.

The importance of monitoring ions is rooted in the technology behind ionization detectors, which are particularly sensitive to fast-flaming fires that emit small combustion particles. This sensitivity allows them to effectively detect smoke from a variety of sources. Hence, the correct answer reflects the operational principle of these detectors, focusing on their interaction with ions in the air rather than other factors like temperature changes or smoke density, which are monitored by different types of detection technologies.