What does an ionization smoke detector specifically detect?

An ionization smoke detector is specifically designed to detect invisible products of combustion, which are produced during the early stages of a fire. These products include small smoke particles generated by fast-burning fires, such as those resulting from paper or wood. The ionization detector uses a small amount of radioactive material to create ions within a sensing chamber. When smoke enters this chamber, the ions are disrupted, altering the flow of current and triggering the alarm. This detection capability makes ionization smoke detectors particularly effective for fires that emit smaller particles, providing an essential early warning in scenarios where fast response is critical.

In contrast, visible smoke is more easily detected by photoelectric smoke detectors, which respond better to larger smoke particles. Heat detectors focus on temperature changes rather than smoke, and carbon monoxide detectors specifically monitor levels of carbon monoxide gas, which is a byproduct of incomplete combustion. Thus, ionization smoke detectors excel in identifying the subtle signs of an incipient fire through the detection of invisible smoke.