Air permeability is the ability of a material or product to allow the transmission of gases or water vapor across its surface or structure.ASTM International (American Society for Testing and Materials) has developed several standard test methods for evaluating the air permeability of materials. The following are some of the commonly used ASTM standards for air permeability testing:

1. ASTM E96/E96M: This standard contains a series of test methods for measuring the water vapor transmission rate and water vapor resistance of materials. There are two main test methods:

   - ASTM E96 Method A: This method is suitable for measuring the water vapor transmission rate of a material. It involves mounting a sample of the material in a permeable test device and applying different humidity gradients on both sides of the sample. The transmission rate is then calculated by measuring the humidity gradient and the water vapor flow rate.

   - ASTM E96 Method B: This method is used to measure the water vapor resistance of a material. It involves mounting a sample of the material in a closed chamber and calculating the water vapor resistance by measuring changes in humidity and temperature.

2. ASTM D737: This standard test method is used to measure the permeability of thin film materials. It involves mounting a sample of the material in a sealed test apparatus and calculating the rate of permeability by measuring the gas flow and pressure differential.

3. ASTM D1653: This standard test method is used to measure the air permeability of textile fabrics. It involves mounting a fabric sample in a specific device and calculating the air permeability by measuring the air flow and pressure difference.

4. ASTM C177: This standard test method is used to measure the gas permeability of insulation materials. It involves mounting a sample of the material in a specific device and calculating the permeability by measuring the gas flow and pressure difference.

5. ASTM F1868: This standard test method is used to measure the water vapor transmission rate of waterproof or moisture resistant materials. It involves mounting a sample of the material in a special test device and calculating the transmission rate by measuring the humidity gradient and water vapor flow.

The ASTM standard for air permeability test is important for evaluating the quality and application of a material in real-world use to improve efficiency, reduce production costs, and ensure the quality of the product.The ASTM standard allows practitioners in a wide range of fields to quickly evaluate the suitability of materials for use in a variety of applications.