This International Standard specifies two methods for determining the air flow value of cellular polymeric flexible materials: . method A, for conventional types of flexible cellular polymeric material; . method B, for all types of flexible cellular polymeric material, but especially for materials with a low permeability to air. NOTE 1 Air flow values can be used to give an indication of the effects of formulation and production variables on the cellular structure. NOTE 2 In this International Standard, the expression "conventional type of flexible cellular polymeric material" means types which are unsuitable for sealing purposes.