National standards refer to national standards. It is a standard approved and released by the national standardization authority, which is of great significance to the national economic and technological development and is unified nationwide.

Our national standards are divided into mandatory national standards (GB) and recommended national standards (GB/T). The number of a national standard consists of the code name of the national standard, the sequence number of the national standard's release and the year number of the national standard's release (year of release).