Humidity-Dependent Air Permeability of Textile Materials1

Changes in fabric structure as hygroscopic fibers swell at high humidities can have a large influence on the measured air permeability of fabrics such as cotton, wool, silk, and nylon. The variation of air permeability as a function of relative humidity is of practical importance in ranking and evaluating candidate textiles for protective clothing applications. This paper describes a test method used to determine the relative humidity dependence of the air permeability of hygroscopic woven textile fabrics. The instru mentation also permits dynamic measurements during a step change in relative humid ity. Typical results are shown for woven fabrics, nonwoven battings, and novel elec trospun fiber mats.