2020 年 23 巻 1 号 p. 31-43
To create an optimal indoor thermal environment, it is necessary to identify the environmental conditions that cause a sensation of dryness. Dryness is experienced in various parts of the human body such as the nose, mouth, throat, eyes, and skin: this study focuses on dryness in the airway. The relationship between the sensation of dryness and environmental factors such as the ambient air temperature and humidity (vapor pressure) was analyzed based on experiments performed on four subjects. This study analyzed the sensation of dryness experienced in six parts along the respiratory tract and the temperature of air inhaled/exhaled at the airway aperture of each of the four subjects under different conditions of humidity and temperature maintained in an artificial climate chamber. The route of respiration was restricted to the nose or the mouth by blocking the other aperture. The experimental results revealed that the temperature of exhaled air was lower and the sensations of dryness in the nose, mouth, and throat were more intense in the case of low humidity under a constant temperature. These results suggest that an increase in the evaporation rate in the airway may cause a sensation of dryness. Further, the experimental results revealed that in the case of high temperature and constant vapor pressure, the sensation of dryness tended to be more intense. This suggests that higher ambient temperature increases the evaporation rate in the airway owing to the increase in the saturated vapor pressure in the inner surface of the airway.