Passive cooling is performed by removing personal protective equipment and other clothing and moving to a cooler environment.

The correct choice, passive cooling, refers to a method used to manage heat stress and reduce body temperature through natural means without the use of active devices. This technique involves removing personal protective equipment (PPE) and clothing, which can help allow the body to cool itself more effectively. By moving to a cooler environment, the body can take advantage of lower ambient temperatures to promote heat loss through convection and evaporation, effectively enabling the natural cooling mechanisms.

This approach is particularly important in firefighting and emergency response scenarios, where personnel are at high risk of overheating due to the strenuous physical demands and protective gear they wear. Passive cooling is often the first step in rehabilitation protocols designed to ensure the safety and health of firefighters during and after intense activities. It allows for gradual recovery and helps to prevent heat-related illnesses.

Other techniques or methods mentioned, such as active cooling, involve using external sources like ice packs or water misting to lower body temperature more rapidly, which is not the focus of this question. Understanding the nuances between these terms is critical for maintaining safety and effectiveness in the field.