ISO 6974-6:2002 describes a gas chromatographic method for the quantitative determination of the content of helium, hydrogen, oxygen, nitrogen, carbon dioxide and C₁ to C₈ hydrocarbons in natural gas samples using three capillary columns. This method is applicable to the determination of these gases within the mole fraction ranges varying from 0,000 1 % to 40 %, depending on the component analysed, and is commonly used for laboratory applications. However, it is only applicable to methane within the mole fraction range of 40 % to 100 %. These ranges do not represent the limits of detection, but the limits within which the stated precision of the method applies. Although one or more components in a sample may not be present at detectable levels, the method can still be applicable.

ISO 6974-6:2002 is only applicable if used in conjunction with ISO 6974-1:2000 and ISO 6974-2:2001.

This method can also be applicable to the analysis of natural gas substitutes. Additional information on the applicability of this method to the determination of natural gas substitutes is also given where relevant.