GB/T 23227-2008 specifies the determination method of Porosity of materials such as cigarette paper and forming paper. The standard covers the test principle, equipment, sample preparation, operation steps and result calculation. It is clear that Porosity is determined by the measurement of the rate of gas through the material under the specified pressure difference by a specific instrument. It provides a unified specification process for the testing of the ventilation performance of Tobacco Encasement materials. It helps to control the mass of the product and meet the requirements of the cigarette production process for the Porosity of related materials.