A LIGHTWEIGHT AMBIENT AIR COOLING UNIT FOR USE IN HAZARDOUS ENVIRONMENTS

Recent research demonstrated (a) the effectiveness of intermittent con ditioned air cooling during rest breaks to significantly reduce cumula tive heat storage and (b) that longer work sessions were possible for individuals wearing chemical defense ensembles. To further advance thi s concept, a strategy for implementing continuous air cooling was conc eived; ambient air cooling was added during work cycles and conditione d air cooling was delivered during rest periods. A compact battery-pow ered beltpack cooling unit (3.9 kg) designed and made at the U.S. Air Force Armstrong laboratory was used to deliver 5.7 L/sec filtered ambi ent air during work cycles: 4.7 L/sec to the body and 1 L/sec to the f ace. Five experimental cycles were conducted in a thermally controlled chamber under warm conditions (32 degrees C, 40% relative humidity) w ith (1) no cooling-intermittent work, (2) intermittent cooling, (3) co ntinuous cooling during intermittent exercise, and (4) no cooling-cont inuous work and (5) ambient air cooling during continuous exercise. in termittent, conditioned, and continuous air cooling resulted in signif icant reductions in rectal temperature, mean skin temperature, and hea rt rate as compared with the no-cooling trials. The continuous air-coo ling trial significantly improved thermal comfort and sweat evaporatio n Results suggest that ambient air delivered during work cycles by a l ightweight portable unit (in conjunction with conditioned air delivere d during rest periods), can definitely improve personal comfort, reduc e skin temperature, and decrease the cumulative fatigue common to repe ated work/rest cycles in selected military and industrial applications in which individuals work in chemical defense ensembles.