This document specifies two methods for determining the air flow value of flexible cellular polymeric 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. For method B two methods are specified in this document: Method B1: with manual measurement Method B2: with automatic measurement 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 document, the expression conventional type of flexible cellular polymeric material means types which are unsuitable for sealing purposes.