This document specifies a method for the determination of low specific surface area of powders ELTs rubber by measuring the amount of physically adsorbed krypton gas and applying the theoretical multipoint Brunnauer, Emmett and Teller (BET) method. This document defines a specific method for powders taking into account that, in order to obtain an accurate value of specific surface area, a representative sample of the material to be tested is taken according to the principle that every particle of the sample that represents the lot have an equal probability of being included in the sample.