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    IMCA updates guidance on surface supplied mixed gas diving operations

    News // November 4, 2005

    The International Marine Contractors Association (IMCA) has published a revised version of ‘Surface Supplied Mixed Gas Diving Operations’ (IMCA D 030), which sets out the limitations of the technique and areas to be covered in dive plans.

    Surface supplied diving using a mixture of helium and oxygen as the breathing gas can be used to increase the range or duration of surface diving operations without the use of saturation techniques. However, in general this technique is not an effective alternative to saturation diving.

    In particular, the dive plan needs to consider all of the relevant safety implications of using this technique instead of a closed bell. The restricted bottom time in the deeper range results in it only being suitable for limited types of work, such as short duration inspection dives or simple tasks, such as disconnecting a wire.

    The guidance document identifies what is generally regarded in the diving industry as good practice to achieve safe working during surface supplied mixed gas diving operations, with the principal areas covered relating to safety considerations, personnel and equipment requirements.

    “The original version of this guidance was prepared by our Asia-Pacific Section and issued in 2003,” explained IMCA’s Technical Director, Jane Bugler. “This has been reviewed by a workgroup comprising representatives of our Americas Deepwater, Asia-Pacific, Europe & Africa and Middle East and India sections re-evaluating use of the technique around the world and the hazards and ways in which they can be avoided.  The result is an updated document, which gives further information on the operational limits of the technique and issues to be considered during risk assessment. A dedicated DESIGN (Diving Equipment Systems Inspection Guidance Note) is currently being finalised to expand our guidance in this area."

    “National Regulations may exist in some parts of the world that limit or exclude the use of techniques outlined in the guidance document – for example by restricting depth," Bugler noted. "In such cases these National Regulations must always take precedence over this guidance publication.”

    The guidance document has sections devoted to safety considerations (operational limits; risk assessment; equipment failure; recovery of an injured diver; and operational method); personnel (divers; supervisors; and manning levels); equipment (diving equipment; decompression facility) as well as sections on the selection of tables; and additional reference sources.

    Copies of IMCA D 030 are available at £5 each (£6 including delivery outside Europe) for IMCA members (who can also download the publication from the IMCA members-only section of the website free of charge) and £10 for non-members via the website at; by email at or from IMCA, 5 Lower Belgrave Street, London SW1W 0NR, UK; Tel: +44 (0)20 7824 5520; Fax: +44 (0)20 824 5521. 

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