This part of ISO 8216 establishes a general system of classification which applies to petroleum fuels designated by the prefix letter “F”.

Within class F, five families (designated as categories) of products are defined according to the type of fuel and listed in decreasing order of volatility. One category, D, is defined further by subgroups on the basis of volatility and flash point, because of the safety implications of different customary titles for such fuels in different parts of the world. Subgroup L (light distillate) is a highly volatile liquid fuel with a closed-cup flash point below normal ambient temperature, and thus may require special hazard precautions not necessary for subgroups M and H.

The detailed classification of a family, taking into account complementary elements according to the uses, type and properties, define particular products in each category, and are given in relevant parts of ISO 8216 as the need arises.