The offshore diving industry uses a variety of gases and gas mixtures in its operations, each of which has distinct qualities, a specific purpose and, of course, hazards. This guidance note sets out a common industry approach to enable anyone working with gas cylinders to be able to clearly identify the nature of the contents by means of the relevant markings on the cylinder or quad and/or from the connection point of large banks where the contents are not visible to the operator.

This note supersedes the 1994 publication AODC 016 on the same subject, which has now been withdrawn. The guidance was fully reviewed and updated in 2007 to reflect current international standards and understanding of the marking of gas cylinders.