Abstract
This report is to present a method to measure air permeability under low flow rate where Darcy's law applies. The air permeability of polyester textile fabrics was measured and the conditions for the measurement was investigated. Test method by ASTM standard instructs to perform the test under a condition of relatively high flow rate. Consequently, the value obtained according to the standard depends upon the pressure difference between the two fabric surfaces. This conflicts with the real physical meaning of the air permeability. However, according to the method presented in this report, it is possible to obtain the value which is independent of the pressure difference.
