The ISO 18473-1:2015 standard defines the properties and test methods of nanoscale calcium carbonate for sealing agent applications. Nanoscale calcium carbonate is an important increment in sealing agents due to its excellent rheology and enhancement performance. The standard specifies in detail the key characteristics of nanoscale calcium carbonate such as size, specific surface area, morphology, and provides a standard method for testing these characteristics. By developing uniform requirements and test methods, ISO 18473-1:2015 aims to improve the performance of sealing agents and promote technical exchange and product conformity within the industry.