The European EN 751 Standard specifies the requirements and testing methods for sealing materials for metallic threaded connections in contact with 1st, 2nd and 3rd family gases and hot water.
The European EN 751 standard consists of three parts.
EN 751-1: Anaerobic adhesives
EN 751-2: Non-curing sealing materials
EN 751-3: Unsintered PTFE tapes