The International Classification for Standards (ICS) is a convention managed by the ISO (International Organization for Standardization) and used in catalogues of international, regional, and national standards.
A very large number of standards exists, covering almost every human activity—packaging and distribution, civil engineering, and many other fields. The ICS provides a hierarchical structure so standards can be found and grouped in a consistent way.
The ICS uses a hierarchical classification with three nested levels: fields (level 1), groups (level 2), and sub-groups (level 3).
Top-level items use a two-digit notation, for example 43 Road vehicle engineering. Sub-groups include the parent levels in their notation, for example 43.040.20 Lighting, signaling and warning devices.
Level 1 (fields)
The first level in the ICS. It may represent a sector of the economy (agriculture, mining), a technology (telecommunications), an activity (environment protection), or a field of science (mathematics). There are currently 40 fields.
Level 2 (groups)
A subdivision of the field.
Level 3 (sub-groups)
Further subdivision into subjects. Most groups include a sub-group 01 for the complete subject and 99 for subjects that do not correspond to other sub-groups.
Level 4 (units)
Not part of the official ICS document, but allowed for users who need to subdivide sub-groups further. Units use a hyphen as a separator, for example 35.220.20-10 Magnetic tapes.