Physiological strain in work with gas protective clothing at low ambient temperature.

Wearing an impermeable gas protective suit (Dräger 500 or 600) and a self-contained breathing apparatus (Dräger PA 80; total weight 27 kg (59.5 lb], seven experienced firemen and one mechanic performed simulated repair and rescue tasks in a chemical plant. The subjects' mean (+/- SD) age, height, weight and estimated maximal oxygen consumption were: 36 +/- 4 years; 181 +/- 6 cm; 83 +/- 8 kg; and 42 +/- 5 mL/min/kg, respectively. The operations took place outdoors (ambient temperature 2.0 degrees C (35.6 degrees F), wind velocity 0-4 m/s). The total work time averaged 37 minutes. During tasks of search, handling vents, and sawing and replacing bolts, the mean (+/- SE) heart rates measured by a Depex recording device were 146 +/- 2, 148 +/- 2, and 147 +/- 5 beats/min, respectively. The mean rectal temperature increased 0.8 degrees C during the whole work period. Weight loss due to sweat averaged 300 g. In conclusion, typical tasks with gas protective clothing caused marked physiological strain among subjects in average physical condition even though the thermal strain was relatively low because the weather was cool. The results emphasized the need to evaluate physical fitness during the periodic check-ups of workers who may have to use gas protective clothing.