OUR PERSONAL COOLING VEST MAINTAINS A COMFORTABLE 65° F TEMPERATURE FOR UP TO 3 HOURS. THE SEMI-SOLID THERMAL ENERGY STORAGE MATERIAL (PCM) IS DESIGNED TO ABSORB HEAT GENERATED BY THE WEARER. A GREAT SOLUTION FOR WORKING IN HIGH HUMIDITY AREAS AND FOR USE UNDER OTHER PPE GARMENTS WHERE EVAPORATIVE PRODUCTS ARE LESS EFFECTIVE.THE PCM MATERIAL IS SET AT A COMFORTABLE TEMPERATURE THAT WILL NOT CAUSE VASOCONSTRICTION. VASOCONSTRICTION IS A PHYSICAL RESPONSE TO EXTREME COLD, WHERE THE VEINS AND ARTERIES CONSTRICT AND SLOW BLOOD MOVEMENT, CAUSING THE BODY TO RETAIN HEAT. 65° IS COMFORTABLE AND LESS SHOCKING TO THE BODY`S SYSTEM, ALLOWING FOR NATURAL CIRCULATION.