This rule stipulates the requirements for compulsory product certification for radionuclide limits of porcelain tile products. The product range applicable to this rule is: porcelain tiles with an average water absorption rate E≤0.5% for building decoration. Porcelain tile products can be certified according to their radioactivity levels as: 1) Category A: unrestricted use; 2) Category B: not for use in the interiors of Class I civil buildings such as residences, senior housing, nurseries, hospitals and schools. surface, but can be used for the exterior cladding of Class I civil buildings and the interior and exterior cladding of all other buildings.