Experimental study of human thermal sensation under hypobaric conditions in winter clothes

Hypobaric conditions, with pressures about 20–30% below that at sea level, are often experienced at mountain resorts and plateau areas. The diffusive transfer of water evaporation increases at hypobaric conditions whereas dry heat loss by convection decreases. In order to clarify the effects of barometric on human thermal comfort, experiments are conducted in a decompression chamber where the air parameters were controllable. During experiments, air temperature is set at a constant of 20, air velocity is controlled at <0.1 m/s, 0.2 m/s, 0.25 m/s, and 0.3 m/s by stages. The barometric condition is examined stepwise for 1atm, 0.85 atm and 0.75 atm of simulated hypobaric conditions, which is equivalent to altitude of 0 m, 1300 m, and 2300 m respectively. Ten males and ten females in winter clothes participate in the experiments. Thermal sensations are measured with ASHRAE seven-point rating scales and skin temperatures were tested at each altitude. The main results are as follows: when the altitude rises, (1) the mean thermal sensation drops; (2) people become more sensitive to draught and expect lower air movements; (3) no significant change of mean skin temperature has been found. The results of the present study indicate that hypobaric environment tends to make people feel cooler.