(a) Fuel Supply Container. Each CNG fuel supply container shall be constructed and inspected in accordance with DOT regulations and shall have a rated service pressure of not less than 2250 psi at 70° F. It shall not be filled beyond the working pressure stamped on the tank and marked near the filler connection, corrected for the ambient temperature at time of filling as prescribed by DOT.

(b) Identification Markings. Each CNG fuel supply container shall have the following identification markings:

(c) Shut-off Valve. A manually operated shut-off valve shall be in direct communication with the container and shall be marked with the words “SHUT-OFF VALVE.” (Decals or stencils are acceptable.) No valve shall be used for CNG unless it has been certified for that purpose by the manufacturer. The shut-off valve shall be securely mounted and shielded or installed in a protected location to prevent damage from vibration and unsecured objects.

(d) Pressure Relief Devices. One or more pressure relief devices shall be installed in the fuel supply container in communication with the fuel and vented to the outside of the vehicle compartment. Relief devices shall be approved as to type, size, quantity, and location by the Bureau of Explosives or meet the DOT Hazardous Materials Regulations in 49 CFR 173.34 and shall have the following permanent identification markings:

(e) Gages. Gages used in CNG systems shall be designed and installed as follows:

(f) Pressure Reducing Regulators. An automatic pressure reducing regulator or regulators shall be installed in CNG systems to reduce container pressure to a value consistent with the working pressure required by the carburetor. Means shall be provided to prevent malfunction due to refrigeration effects. Regulators shall be installed so that their weight is not placed on, or supported alone by, the attaching line or lines. Regulators shall be designed to a container's maximum working pressure and temperature with a pressure safety factor of not less than four.

(g) Vents. Every compartment in which a CNG container is installed shall be vented to the atmosphere, unless all piping and connections are exterior to the compartment or vapor sealed and vented to the atmosphere. The vent or vents shall be installed at the highest practicable point of the compartment and shall have an open area totaling not less than 3 sq in.