GB/T 7702.20-2025 is part of the "Test Methods for Granular Activated Carbon from Coal" series of standards. It specifies a unified method for determining the total pore volume and specific surface area of activated carbon through gas adsorption, typically using the BET method. The standard details the principles of the determination, sample pretreatment, testing procedures, and reporting of results, aiming to provide a reliable basis for quality control, performance evaluation, and trade of activated carbon products. This revision includes additional conditions for sample pretreatment and detailed specifications for degassing procedures, intended to enhance the consistency and reproducibility of test results. Completing the test generally requires the use of core detection instruments such as specific surface area and porosity analyzers (also known as physisorption analyzers) or fully automated specific surface area and micropore analyzers.