A MODEL OF EVAPORATION FROM THE SKIN WHILE WEAVING PROTECTIVE CLOTHING

A simple model was developed to describe the transport of water vapour from subjects working in hot environments while wearing chemical-prot ective clothing. The goal of the modelling was to obtain a better esti mate of evaporative cooling of the subjects, as it was hypothesised th at calculations of evaporative heat loss based on changes in dressed w eight over-estimate the actual benefit experienced by the subjects. Th e model employed measured values of vapour pressure within the clothin g ensemble to estimate the skin vapour pressure. The resistance of the clothing ensemble to water vapour transport was calculated from measu rements of the physical properties of the materials in conjunction wit h estimates of the resistance of air layers between the clothing layer s. The model predicts mean evaporation rates from the skin that are ap proximately 60% of those calculated from measured changes in dressed w eight. Error analysis failed to account for the magnitude of this diff erence and possible explanations for the difference are advanced. A br ief examination of the effect of wicking suggests that some of the dif ference results from a reduction of the resistance of the garment to w ater vapour due to wicking of liquid sweat through fabric layers.