This International Standard provides guidelines for the determination of the total specific external and internal surface area of disperse or porous (pore diameter ) fine ceramic materials by measuring the amount of physically adsorbed gas according to the method of Brunauer, Emmet and Teller (BET method) [1]. General guidelines of the method are described in ISO 9277. This International Standard only focuses on specific details relevant to fine ceramic materials. It should further be noted that the BET method cannot be applied to type I isotherms (microporous materials or chemisorption behaviour) or when the solid absorbs the measuring gas. NOTE For further details on those subjects please see IUPAC references [2], [3] or the textbook by Gregg and Sing [4].