The aim of this International Standard is to provide manufacturers, vehicle operators, fuelling station operators and others involved in the compressed-natural-gas vehicle industry with information on the fuel quality for natural gas vehicles (NGVs) required to develop and operate compressed-natural-gas vehicle equipment successfully. Fuel meeting the requirements of this International Standard should: a) provide for the safe operation of the vehicle and associated equipment needed for its fuelling and maintenance; b) protect the fuel system from the detrimental effects corrosion, poisoning, and liquid or solid deposition; c) provide satisfactory vehicle performance under any and all conditions of climate and driving demands. Some aspects of this International Standard may also be applicable for the use of natural gas in stationary combustion engines.