What is Air permeability ? Air permeability is an important factor in the performance of such textile materials as gas filter, fabrics for air bags, clothing, mosquito netting, parachutes, sails, tent age, and vaccum cleaners. It can also be used to provide an indication of the breathability of weather-resistant and rainproof fabrics. Construction factors and finishing techniques can have an effect upon air permeability by causing a change in the length of airflow paths through a fabric.Fabrics with different surface textures on either side can have a different air permeability depending upon the direction of air flow. Air permeability tester Test Procedure: 1、Suction pump ‘A’ draws air through the test specimen ‘S’ at 20±2oC and 65±2% R.H. The rate of flow is controlled by the by – pass valve ‘B’ and the series valve ‘C’. 2、The rate of flow is adjusted until the required pressure drop across the fabric is indicated on a draught gauge ‘D’ which is graduated from 0 ...