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    IMCA issues diving gas cylinder/storage colour coding advice

    Publications // December 21, 2007

    Colour coding is used primarily to identify the hazard associated with the contents of a cylinder. Individual cylinder labelling is the primary means of identifying the contents of the cylinder which could be a gas that may be supplied direct to the diver; or one that may not be supplied direct to the diver but is manufactured to diving quality standards for incorporation into breathing mixtures.

    Its importance cannot be over-emphasised, and this has led to the International Marine Contractors Association (IMCA) publishing guidance on ‘Marking and Colour Coding of Gas Cylinders, Quads and Banks for Diving Applications’. 

    “The title of the guidance explains exactly what the new publication is about,” said Jane Bugler, Technical Director of IMCA. “The objective of this new guidance is 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.”

    The guidance (IMCA D 043) is applicable internationally, but, national regulations/standards will normally prevail. There are many national standards, codes, guidance and information sheets available, pertaining to the marking and colour coding of gas cylinders which may be used in diving operations.

    In addition to commenting on this, the guidance has a useful chart showing commonly accepted colour coding for helium, medical oxygen, oxygen and helium mixtures, nitrogen, oxygen/helium/nitrogen mixtures, air (breathing), oxygen/nitrogen mixtures, carbon dioxide, and calibration gases.

    It also illustrates gas mixtures for medical or inhalation purposes; and shows typical examples of quads and banks (in addition to carrying written descriptions) and also of a cylinder labelling system.

    “Sampling of all gases must be carried out prior to the commencement of, and during, diving operations,” emphasised Bugler. “Gas cylinders and quads, as received from the supplier, should have a label attached and a purity certificate stating the composition of the gas they contain. However, it must be stressed that analysis of gas as received from a supplier at a diving installation or site is the responsibility of a nominated and competent individual; and that the ultimate authority for establishing the exact contents of any gas cylinder, bank or unit before use rests with the relevant supervisor.”

    The guidance can be downloaded free of charge by IMCA members on the members-only website. Printed copies cost £2.50 for members and £5.00 for non-members (plus 20% for delivery outside Europe) from; from IMCA at 5 Lower Belgrave Street, London SW1W 0NR, UK. Tel: 020 7824 5520; Fax: +44 (0)20 7824 5521; Email:



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