Before revision: ANSI/ASME Standards In the United States, Occupational Safety and Health Administration regulations recommend following American Society of Mechanical Engineers Standard A13.1-2015 - Scheme for the Identification of Piping Systems.
After revision: United States standardsANSI/ASME Standards In the United States, Occupational Safety and Health Administration regulations recommend following American Society of Mechanical Engineers Standard A13.1-2015 - Scheme for the Identification of Piping Systems.