This part of ISO 15501 specifies the minimum safety requirements applicable to compressed natural gas (CNG) on-board fuel systems intended for use on the types of motor vehicles defined in ISO 3833. This part of ISO 15501 is applicable to vehicles using compressed natural gas as defined in ISO 15403, including bi-fuel, original-production and converted vehicles.

Matters relating to the skills of installers and converters are outside the scope of this part of ISO 15501.