This International Standard specifies a method for the determination of the nitrogen surface area (NSA) of carbon blacks and other rubber compounding ingredients, like silicas and zinc oxides, based on the Brunauer, Emmett and Teller (BET) theory of gas adsorption using a multipoint determination. This test method specifies the sample preparation and treatment, instrument calibration, required accuracy and precision of the experimental data, and calculation of the surface area results from the data obtained. Also given is a procedure for calculating the statistical thickness surface area (STSA), otherwise known as the external surface area. The test method specified uses an automatic static-volume vacuum apparatus, the surface area being calculated using the BET theory based on monolayer measurements. The method can also be used for verifying “single-point” procedures described in ISO 4652-1 and other standards. The automatic instruments described in these standards perform all the necessary computations, including that of the surface area based on statistical thickness. However, the automatic point-setting procedures used are not applicable to the STSA method. NOTE Automatic instruments based on continuous flow using mixtures of nitrogen and helium gas in various ratios are also available. As good as they are, it is highly desirable to verify their accuracy of measurement against results obtained from vacuum-type instruments.