The effect of relative humidity on physiological equivalent temperature in hot environment

The important meteorological parameter affecting the human energy balance in heat strain condition is the relative humidity. The aim of this paper is to investigate the effect of relative humidity on human heat comfort. In this paper, the physiological equivalent temperature (PET) calculating program was corrected. The relationship between PET and relative humidity, thermal state of human body on a typical hot day was analyzed. The results show that: Sweating is the most effective thermoregulatory process when the body is in a condition of heat strain; High water vapor pressure can restrain sweat evaporation and effect human heat balance in hot environment; The PET value increases rapidly as relative humidity over "threshold value" in hot environment, and the "threshold value" is different in various heat stain condition; The PET calculated by modified program agrees well with heat thermal sensation of people in hot-humidity environment.