What document must specify the standards for devices fitted to each cylinder?

The correct answer emphasizes the importance of manufacturer and OEM specifications in ensuring that any devices fitted to CNG cylinders comply with specific performance and safety standards. OEM, or Original Equipment Manufacturers, often outline detailed requirements and configurations for manufacturing components, including those for CNG cylinders. These specifications are crucial for maintaining compliance with safety regulations and operational efficiency since they are determined by the expertise of the manufacturers that design and build the equipment.

This documentation is essential because it typically includes not only safety guidelines but also operational limits, maintenance requirements, and installation instructions that are tailored to the specific devices and cylinders. By adhering to these specifications, drivers and operators can ensure that the components used are not just compatible but also meet the necessary operational safety standards required for safe and efficient delivery of CNG.

While other options may contain relevant standards or guidelines, they do not specifically encompass the tailored requirements that the manufacturer and OEM provide for individual devices attached to the cylinders.