What must pressure relief devices conform to when used in CNG cylinders?

Answer: B — CGA S-1.1 standards

Pressure relief devices used in CNG cylinders must conform to CGA S-1.1 standards. These standards are established by the Compressed Gas Association and specifically address safety and performance criteria for pressure relief devices in various gas applications, including CNG. Compliance with CGA S-1.1 ensures that the devices can effectively manage pressure changes and safely relieve excess pressure within the cylinder, which is critical for preventing catastrophic failures. The CGA S-1.1 standards take into account various factors, including the construction and testing of the relief devices, to ensure reliability and safety in the handling of compressed gases. Adhering to these standards is essential for ensuring not only the integrity of the gas storage systems but also the safety of the operators and the environment. While other options like ASME Code requirements and DOT regulations are also relevant to certain aspects of pressure vessel safety and transportation regulations, the specific requirement for pressure relief devices in CNG cylinders is best addressed by the CGA standards. ISO 9001 relates to quality management systems rather than specific safety standards for pressure relief devices.