Relative humidity (RH) of a space will affect the rate of evaporation from the skin. The RH is the ratio of the partial
pressure (or density) of the water vapour in the air to the saturation pressure (or density) of water vapour at the same
temperature and the same total pressure [15]. At high air temperatures (approaching average skin temperature of 34
°C) evaporation heat loss is important to maintain comfort. Human occupants are sensitive to the variation of
temperature rather than relative humidity [16] and there is little conclusive evidence to show that either high or low
humidity is detrimental to the health of normal people. However, some studies (e.g. [17]) indicate that people, when
exposed to low relative humidity conditions, may develop dry and irritated skin, mainly due to the increase in
evaporation rate from the skin. A study conducted by [18] on thermal comfort at high relative humidity shows that
there are no significant psychological or physiological differences in human response to exposure of between 60%
to 90% relative humidity for the temperature range of 20ºC to 26ºC while sedentary.