Interlaboratory proficiency tests in measuring thermal insulation and evaporative resistance of clothing using the Newton-type thermal manikin

Clothing acts as an important barrier for heat and vapour transfer between a human body and the environment. Parameters that could describe that transfer include, i.a. the thermal insulation (the so-called dry heat exchange) and the evaporative resistance (the so-called wet heat exchange). Once the above mentioned parameters are determined, it is possible to consciously adapt clothing ensembles to the existing thermal environment in the workplace. In order to validate the mentioned method of thermal insulation and evaporative resistance measurements, the proficiency tests (PT) were organised. The main goal of the PT was to compare thermal insulation and evaporative resistance for one set of clothing using the Newton-type thermal manikin. In total, 4 laboratories participated in the PT study. The reference value of the thermal insulation (It) and evaporative resistance (Ret) were calculated as the mean of all the results. The assessment criteria included: a permissible error for thermal insulation and evaporative resistance measurements was 4% and 10%, respectively. Calculations included, i.a., z-scores and indicators, such as the interlaboratory coefficient of variation or the reproducibility limit. The results contribute to the worldwide discussion on standardised studies of evaporative resistance of clothing.