This International Standard specifies a method for the determination of the permeability of flexible cellular polymeric materials to air flow. It is applicable to test pieces cut from products of cellular material. NOTE — ISO 7231, Polymeric materials, cellular flexible — Method of assessment of air flow value at constant pressure drop,1) specifies a simple quality control method which is also based on the flow of air through cellular materials. This can be used when it is not the intention to calculate the intrinsic properties of various materials in order to compare them, but merely to control the quality of a given cellular material.