Which false statement best describes ionization smoke detectors?

The correct choice highlights a common misconception about ionization smoke detectors. These devices are designed primarily to detect particles produced by combustion; they do not detect carbon monoxide. Ionization smoke detectors work by using a small amount of radioactive material to ionize air in a sensing chamber, creating a current. When smoke enters the chamber, it disrupts this current, triggering the alarm.

In contrast, other options present characteristics or facts that align with the intended use of ionization detectors. They are not sensitive to non-combustible gases, as their design focuses on detecting combustion products rather than gas. They are especially effective at responding to fast flaming fires because such fires produce large amounts of small smoke particles that can scatter the ionizing radiation. Lastly, while the use of radioactive materials is a crucial aspect of their operation, it is not a false statement about them.

Therefore, the assertion that ionization smoke detectors can also detect carbon monoxide is incorrect, making it the best choice for describing a false statement regarding their functionality.