This Standard specifies requirements for natural gas (CNG) fuel systems for engines mounted on motor vehicles, either for the propulsion of the vehicles or for driving some auxiliary function, e.g. a mixer or a pump. It provides requirements for the design and construction of component parts, and for their installation in vehicles, and for tests, commissioning, and periodic inspection.The Standard may be applied to stationary engines and small engine-powered appliances such as floor sweepers, polishers and trolleys, where it is relevant.This Standard does not apply to other natural gas usage, such as the gas supply system for appliances in caravans, mobile homes or for the propulsion of marine craft.This Standard does not cover the areas where major structural modifications are to be carried out to the vehicle (major structural modifications are those not defined in Clause 1.7). Prior to commencement of such work guidance should be sought from the vehicle manufacturer or a professional engineer who is experienced in the automotive disciplines.