WORK TOLERANCE AND PHYSIOLOGICAL-RESPONSES TO THERMAL ENVIRONMENT WEARING PROTECTIVE NBC CLOTHING

Six young, healthy male subjects performed a series of experiments in a climatic chamber in different environmental conditions wearing prote ctive ventilated NBC clothing. Ambient temperature, TA, ranged from -2 0 to 35 degrees C, relative humidity, RH, from 20 to 85%, and air velo city, VA, from 0.1 to 5.0 m s(-1). In addition, thermal radiation, mea sured by the temperature of the globothermometer, TG, was artificially increased in some experiments. A total of 32 experiments were perform ed. The subject had to exercise on a bicycle ergometer at a mechanical power of 60 W for 120 min. Heart rate, HR, oxygen uptake, VO2, Skin t emperature, T-sk, and rectal temperature, T-re, were measured during t he experiments together with the temperature of the space between skin and garment, T mu. Sweat loss was determined as the difference of the body weight before and after the experiment. T mu was well correlated with the chamber environmental parameters. During heat exposure work duration began to decrease progressively from a T-mu > 30 degrees C, r educing to 40 min at the highest thermal load. About the same value of T mu marked the departure of HR, VO2, T-sk and T-re from the values m easured during the same work load in neutral conditions. Also, during cold exposure at -20 degrees C work duration was reduced below I h, bu t the limit appeared to be the cold at the extremities. From these fin dings it appears that T-mu is a good indicator of the thermal load and is related to the environmental condition by the equation: T mu = 9.9 3 +/- 0.56 TA + 0.023 TG + 0.14 RH (T in degrees C, RH in %). For bett er comfort and performance T-mu should be monitored whenever a subject has to work wearing an NBC garment and the ventilating system must be adequate to fulfil the needs imposed on the subject by an adverse env ironment, in particular a high relative humidity.