What feature is distinctive about an air-cooled vest?

An air-cooled vest is specifically designed to manage body temperature by utilizing cool air to draw heat away from the body. This cooling method relies on airflow; as external air circulates through the vest, it carries heat away from the skin, thereby maintaining a cooler body temperature. This characteristic effectively helps individuals working in hot environments or engaged in strenuous activities to prevent overheating.

The other options describe features not associated with air-cooled vests. For instance, encapsulation for thermal protection typically relates to different types of protective gear designed to shield from extreme temperatures, while pumping chilled fluids is characteristic of liquid-cooled vests rather than air-cooled ones. Additionally, using ice for cooling directly relates to ice vests, which operate differently than air-cooled technology.