Evaluation of Personal Cooling Systems in Conjunction with Explosive Ordnance Disposal Suits

Abstract : This study examined the capabilities of three technologies (a liquid cooled undergarment, a thickly- ribbed vest of hydrophylic nylon, and an air vest) to alleviate thermal strain in personnel working in Explosives Ordnance Disposal (EOD) clothing under environmental conditions of 18 deg C and 40% relative humidity (rh), 340 C and 40% rh, and 34 deg C and 80% rh. Simulated EOD tasks consisted of treadmill walking (10 min), unstacking/carrying/stacking weighted boxes (10 min), and a rest period (15 min) with the EOD helmet and jacket removed repeated for a target duration time of 90 min. Physiological data included rectal temperature, Skin temperature, heart rate, sweat production and evaporation, metabolic rate, and subjective evaluations of thermal comfort and perceived exertion. The results indicated that wearing the EOD suit produces significant increases in thermal physiological strain over performing the same tasks in a standard station uniform. However, the liquid-cooled Exotemp personal cooling system was very effective in reducing that strain during heat exposure. Rectal temperatures, heart rates and fluid losses (dehydration) were reduced back to values comparable to those when not wearing the EOD suit, while skin temperatures were actually lower with the cooling system than with only the station uniform. Subjects indicated reduced perceived exertion levels and improved thermal comfort when wearing the liquid-cooling garment with a EOD suit. In contrast, the ribbed vest and air vest showed no significant benefits with the EOD suit. It is concluded that the increase in thermal physiology strain, resulting from wearing the EOD suit during EOD work in hot environments can effectively be minimised by use of Exotemp personnel cooling system.