This part of ISO 15500 specifies tests and requirements for the check valve, a compressed natural gas
(CNG) fuel system component intended for use on the types of motor vehicles defined in ISO 3833.
This part of ISO 15500 is applicable to vehicles (mono-fuel, bi-fuel or dual-fuel applications) using
natural gas in accordance with ISO 15403 (all parts). It is not applicable to the following:
a) liquefied natural gas (LNG) fuel system components located upstream of, and including,
b) fuel containers;
c) stationary gas engines;
d) container-mounting hardware;
e) electronic fuel management;
f) refuelling receptacles.