Final answer:
The primary inspection guidance document for CNG cylinders is FMVSS 304, which provides regulatory requirements and testing procedures.
Step-by-step explanation:
When inspecting CNG cylinders, the primary inspection guidance document is the FMVSS 304 Standard. FMVSS 304, which stands for Federal Motor Vehicle Safety Standard No. 304, provides the regulatory requirements and testing procedures for compressed natural gas (CNG) cylinders used in motor vehicles.
Gaining compliance with FMVSS 304 ensures that CNG cylinders meet the necessary safety standards and can safely store and transport compressed natural gas. This standard includes specifications for materials, construction, performance, labeling, and testing of CNG cylinders.
CNG cylinder manufacturers and vehicle manufacturers rely on FMVSS 304 to ensure the safety and integrity of CNG systems in vehicles. It is an essential document in the inspection and certification process for CNG cylinders.