Efficacy of Liquid, Air, and Phase Change Material Torso Cooling During Light Exercise While Wearing NBC Clothing

Abstract : This study compared the thermoregulatory responses with liquid, air and phase change material (PCM) torso cooling during light exercise at 40 deg C while wearing NBC protective clothing. The liquid-(LC) and air-cooling (AC) systems were powered from external portable chiller units. The PCM cooling vests, which were supplied by Microclimate Systems Incorporated, were worn under the NBC overgarment and were tested with a vertical (CVV) and horizontal (CVH) design. Seven males (29 yrs, 75.6 kg, 1.78 m) performed a no cooling (NC) and 4 cooling trials while walking at 3.5 km.h-1 on a treadmill in the environmental chamber. During the NC condition, tolerance times were 100 min and final core temperature was 39.1 deg C. For the PCM trials (CVV and CVH), tolerance times were extended by 30 min but core temperature still rose to reach values close to 39.0 deg C indicating that the cooling vests could only delay the exhaustion from the heat exposure. However, with both the LC and AC trials, all subjects completed 180 min of exercise and they could of continued longer given that their core temperatures were still below 38.0 deg C. The results have shown that the PCM cooling vests are of benefit for work tasks that continue between 1 to 2 hours but these vests are not as effective in reducing the heat strain of wearing NBC clothing in hot environments as liquid- or air-cooling systems.