Effects of extremely low humidity on comfort and fatigue of Japanese occupants

Subjective experiments were carried out in a climate chamber using Japanese subjects, in order to evaluate human comfort at very low humidity. Two levels of absolute humidity were set. Three air temperature conditions for each absolute humidity level were examined. People were exposed in a chamber for 90 minutes with sedentary activity. Subjective break up time got significantly shorter at extremely low absolute humidity. Air temperature had great impact on subjective general humidity sensation under the conditions set for this experiment. General dryness sensation at low absolute humidity was significantly greater than that at high absolute humidity with same air temperature. Subjects felt their eyes were dryer at low air temperature at the same moisture content in air. In case of the constant air temperature, low absolute humidity caused greater eye dryness sensation. Subjective humidity discomfort of females was greater than male. Very low humidity air dry up the human mucous membrane. Half of subjects perceived their palm of hand as wetted segment even at extremely low humidity. They could feel more tired at low humidity under the cool and thermally neutral condition, while they complained more at high humidity in hot environment. It was found that females tended to be more tired than males even under the same condition.