ISO 15500-4:2012

ISO 15500-4:2012 specifies tests and requirements for the manual valve, a compressed natural gas (CNG) fuel system component intended for use on the types of motor vehicles defined in ISO 3833.
ISO 15500-4:2012 is applicable to vehicles (mono-fuel, bi-fuel or dual-fuel applications) using natural gas in accordance with ISO 15403.
It is not applicable to the following:

        liquefied natural gas (LNG) fuel system components located upstream of, and including, the vaporizer;
        fuel containers;
        stationary gas engines;
        container-mounting hardware;
        electronic fuel management;
         refuelling receptacles.