Which type of smoke detector is most likely to be influenced by air velocity?

The smoke detector that is most likely to be influenced by air velocity is the ionization smoke detector. This type of detector uses a small amount of radioactive material to ionize air in a sensing chamber, which creates a current. When smoke enters the chamber, it disrupts the ionization process, triggering the alarm.

Air velocity can significantly impact the performance of ionization detectors. High air movement can carry smoke away from the detector before it has a chance to enter the sensing chamber and cause a reaction. This means that in environments where there are fans, open windows, or other sources of airflow, ionization smoke detectors might fail to detect smoke in a timely manner, leading to potential safety issues.

In contrast, photoelectric smoke detectors, which utilize a light beam and photo sensor to detect smoke, are less affected by air velocity because their detection relies on the scattering of light rather than ionization. Heat detectors respond to temperature changes and are not influenced by smoke or air velocity in the same way. Ultrasonic devices do not relate directly to smoke detection and instead use sound waves, meaning they do not fit the context of the question regarding smoke responses.