The most basic and most widely used form of cooled personal protective equipment (PPE) is vests that use phase change material (PCM) for thermal energy storage.

The effects of heat stress range from simple discomfort to life-threatening illnesses such as heat stroke. Aside from the environmental factors (such as temperature, humidity, air movement, and radiant heat), the person’s work regimen and clothing requirements are also factors that determine the risk of heat strain.