Effectiveness of an air-cooled vest using selected air temperature and humidity combinations.
We evaluated the effectiveness of an air-cooled vest in reducing thermal strain of subjects exercising in the heat (49 degrees C dry bulb (db), 20 degrees C dew point (dp] in chemical protective clothing. Four male subjects attempted 300-min heat exposures at two metabolic rates (175 and 315 W) with six cooling combinations--control (no vest) and five different db and dp combinations. Air supplied to the vest at 15 scfm ranged from 20-27 degrees C db, 7-18 degrees C dp; theoretical cooling capacities were 498-687 W. Without the vest, endurance times were 118 min (175 W) and 73 min (315 W). Endurance times with the vest were 300 min (175 W) and 242-300 min (315 W). The five cooling combinations were similarly effective in reducing thermal strain and extending endurance time, although there was a trend for the vest to be more effective when supplied with air at the lower dry bulb temperature. At 175 W, subjects maintained a constant body temperature; at 315 W, the vest's ability to extend endurance is limited to about 5 hours.
D000328:Adult; D001831:Body Temperature; D006339:Heart Rate; D006358:Hot Temperature; D006801:Humans; D006813:Humidity; D008297:Male; D008889:Military Personnel; D010807:Physical Endurance; D005082:Physical Exertion; D011481:Protective Clothing; D013312:Stress, Physiological / Q000517:prevention & control; D013546:Sweating