Proposition on a new WBGT index based on 50% relative humidity agreeing with a human sense in living environment

Abstract

The numerical value of Wet-Bulb Globe Temperature WBGT is lower than the air temperature in the summer hot environment. This index does not necessarily agree with a human sense in living environment. The objective of this paper is to introduce a new WBGT index which meets a human sense. Gagge (1976) proposed the straight line giving equal WBGT on the psychrometric chart. The numerical value of WBGT is the temperature at relative humidity 100% on the chart. The humidity 100% as the standard was changed and the temperature in case of relative humidity 50% was defined as new index WBGT50. When WBGT is 31°C after a relation between WBGT and WBGT50 was calculated, WBGT50 will be 36°C. The proper numerical value is indicated to show danger of heat exhaustion, and this index is thought to be useful.