Abstract
The physiological and subjective responses of six sedentary subjects wearing half-facepicce respirators were observed over a wide range of room and respirator air conditions. Room air and dew-point (Ta:Tdp) temperatures were 25:11°, 30:13°, and 35.16°C in still air. Respirator air temperatures were maintained independently of room conditions at 27°, 30°, 33°, and 36°C with relative humidity levels of 47% and 73%. Physiological measurements included local skin and dew-point temperatures. Subjective judgments of acceptability, thermal sensation, degree of discomfort, sense of skin moisture, and difficulty of breathing were recorded separately for the thermal environment in the room and inside the respirator. Respirator temperatures cooler than 33°C were always comfortable and 100% acceptable; respirator air temperatures above 33°C or higher humidity levels decreased respirator acceptability. Acceptability of the respirator environment decreased as lip temperature increased above 34.5°C or when respirator dew-point temperature increased above 20°C. Increased respirator air temperature and humidity often made breathing seem “slightly hard.” The respirator conditions influenced the subjects' judgment of the acceptability of the surrounding thermal environment.