Perspectives in Microclimate Cooling Involving Protective Clothing in Hot Environments

The effectiveness of microclimate cooling systems in alleviating the thermal burden imposed upon soldiers by the wearing of chemical protective clothing under varying environmental conditions has been examined in a series of studies conducted by the U.S. Army Research Institute of Environmental Medicine on the copper manikin, in the climatic chambers and in the field. Liquid-cooled undergarments (LCU) and air-cooled vests (ACV) were tested under environmental conditions from 29 C, 85% rh to 52 C, 25% rh. These parameters were chosen to stimulate conditions which may be encountered in either armored vehicles,or in desert or tropic climates. We have reviewed seven studies using LCU (including two ice-cooled vests) and six studies using ACV. LXU tests investigated the effect on cooling when the proportion of total skin surface covered by the LCU was varied. ACV tests examined the effects on cooling during different combinations of air temperature, humidity and air flow rates. Additionally, these combinations were tested at low and moderate metabolic rates. The findings from these LCU and ACV studies demonstrate that a) cooling can be increased with a greater body surface coverage by a LCU and b) evaporative cooling with an ACV is enhanced at low metabolic rates with optimal combinations of air flow rates and dry bulb/dew point temperatures, resulting in the extension of tolerance time. The application of these findings to industrial work situations is apparent.