The aim of ISO 15403-1:2006 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 ISO 15403-1:2006 should provide for the safe operation of the vehicle and associated equipment needed for its fuelling and maintenance, protect the fuel system from the detrimental effects of corrosion, poisoning, and liquid or solid deposition and provide satisfactory vehicle performance under any and all conditions of climate and driving demands. Some aspects of ISO 15403-1:2006 may also be applicable for the use of natural gas in stationary combustion engines.