Portable, Ambient Air Microclimate Cooling in Simulated Desert and Tropic Conditions

The feasibility of providing ambient air during exercise and conditioned air during rest on reducing physiological strain and optimizing tolerance time was examined. Six male soldiers attempted 250-min exposures in hotdry and hotwet environments. Subjects wore chemical protective clothing over the combat vehicle crewman uniform and an air-cooled vest. They alternated between 50 min of treadmill walking and 50 min of rest. During the walks, a backpack mounted blower provided a total of 10 or 18 cfm of air to the vest and face while subjects received 18 cfm of conditioned air from an umbilical during rest. In the hotwet environment, tolerance time was extended compared to a predicted tolerance time assuming no microclimate cooling. We concluded that the ambient air backpack reduced physiological strain and improved tolerance time of combat vehicle crewman during exercise in the heat. In addition, since the physiological and tolerance time responses with the 10 cfm airflow were midway between the control and 18 cfm airflow results, further tests may find an intermediate airflow rate which significantly improves performance while minimizing the backpack blower size. Keywords Heat stressPhysiology.