Evaporation of Sweat on Clothed Subject

Because of its excellent protective effect against radiant heat, clothing is considered to be useful for workers in a hot industrial shop. But, it is also likely that clothing acts as a barrier to evaporative heat loss and is disadvantageous to the heat regulation of workers. For instance, Belding et al.1) have shown that metalic-coated clothing having an excellent protective effect against heat load, may give rise to more heat strain, if it does not permit ventilation and consequent evaporation of sweat. So clothing for workers in a hot industrial shop should be able to accerelate evaporative heat loss. But satisfaction of this requirement seems to be difficult, because evaporative heat loss on a clothed subject is very complicated and little has been known about it. In a hot industrial shop, however, most people are working in sweat and their evaporative heat losses are mainly due to evaporation of sweat, therefore the blocking effect of clothing upon evaporation of sweat is at first to be studied. Much existing information on water or vapor permeability of various sorts of fabrics may be available, but most of them are obtained from tests on a piece of fabric and they do not necessarily agree with tests observed on a clothed subject as indicated in many studies on thermal insulation of clothing. In this study, the movements of sweat from its production to its evaporation was observed on subjects in the nude and with various sorts of clothing.