Heat strain imposed by toxic agent protective systems

This study evaluated physiological heat strain from two developmental toxic agent protective systems compared with the standard Toxicological Agent Pr otective (TAP) suit during exercise-heat stress. Eight subjects (six men, t wo women) completed three experimental trials, at 38 degreesC, 30% rh, wear ing: 1) Self Contained Toxic Environment Protective Outfit (STEPO) with reb reather (STEPO-R); 2) STEPO with tether (STEPO-T] or 3) the standard TAP. T he STEPO systems provided effective body cooling of: STEPO-R, 200 +/- 36 W; and STEPO-T, 186 +/- 59 W. TAP had no cooling. All experimental trials use d treadmill walking at 0.89 m . s(-1), 0% grade at exercise/rest cycles of 20/10 min for 240 min. Metabolic rates for the treatments were: STEPO-R, 29 8 +/- 26 W; STEPO-T, 299 +/- 34 W; and TAP, 222 +/- 40 W. Rate of heat stor age was lear (p < 0.05) in STEPO-R (37 +/- 8 W . m(-2)): and STEPO-T (38 +/ - 12 W . m(-2)) than in TAP (77 +/- 15 W . m(-2)). Sweating rate was less ( p < 0.05) in STEPO-T (10.0 +/- 4.8 g . min(-1)) than in TAP (23.8 . 11.4 g . min(-1)). There was no difference between STEPO-R (12.3 +/- 5.6 g . min(- 1)) and the other two uniform systems. Subjects did not complete targeted e xposure times of 240 min. Exposure time was longer (p < 0.05) in STEPO-R (8 3 +/- 22 min) and STEPO-T(106 +/- 39 min) than in TAP (46 +/- 10 min). Pred icted time to 39.0<degrees>C was less (p < 0.05) in TAP (69 +/- 20 min) tha n in either STEPO-R (226 +/- 124 min) or STEPO-T (244 +/- 170 min). The res ults of this study show that cooling in STEPO significantly reduced heat st orage relative to TAP. The new generation toxic cleanup uniform systems eff ectively reduced heat stress and increased work capabilities compared with the standard TAP suit.