This part of ISO 15901 describes methods for the evaluation of the volume of micropores (pores of internal width less than 2 nm) and the specific surface area of microporous material by low-temperature adsorption of gases [1],[2],[3],[4],[5],[6],[7]. These are comparative, non-destructive tests. The methods use physisorbing gases that can penetrate into the pores under investigation. The method is applicable to isotherms of type I, II, IV or VI of the IUPAC classification (see ISO 15901-2:—, Figure 1, and ISO 9277). The methods in this part of ISO 15901 are not applicable when chemisorption or absorption takes place.