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Bell diving (also called mixed gas diving and saturation diving) is diving from a closed bell using mixed gas and hot water suits and is generally performed in very deep water offshore.

Differing from air diving (also called open bell or wet bell diving) which is performed to depths of down to 50m, bell diving depths are usually below 50m and can be down to 300m. However, it is becoming more common for closed bell divers to work in shallower water (shallow sat) as it enables substantially extended work periods.

Unlike other divers who return back to the surface on completion of a work shift, bell divers are recovered to a dry chamber system in which they live for extended periods of time—normally no less than 10 days and averaging 28 days.


  • Since gaining the ADAS Part 3 diving qualification or equivalent, have completed at least 50 dives for a minimum total bottom time of 50 hours and have recorded and had certified by a qualified Supervisor these dives in a formal divers’ daily logbook in a format in accordance with, or similar to that required by, ADAS;
  • All of the dives must have been conducted in surface supplied equipment and in open water. i.e. not in compression chambers, pools, and tanks;
  • No dives undertaken as part of a training and/or assessment courses are to be counted;
  • 10 hours of the bottom time is to be at depths greater that 20 metres;
  • At least 6 hours of that 10 hours bottom time is to be at depths greater that 30 metres;
  • Only bottom time is to be counted towards the 50 hours. i.e. decompression stop time is not to be included;
  • No dive shorter than 15 minutes bottom time is to be counted;
  • In a dive where the bottom time is longer than 2 hours only 2 hours is to be counted;
  • Hold a valid certificate of medical fitness to dive issued in accordance with AS 2299.1;
  • Hold a valid certificate of competence in first aid at work, issued by an organisation whose training and qualifications are approved by ADAS in accordance with relevant Australian arrangements, including a CPR and Oxygen Administration certificate issued within the last 12 months;
  • The certificates above are to be “in date” for the whole of the closed bell diving assessment period.


Training for ADAS Bell Diver is only offered at The Underwater Centre Tasmania. The course runs for 3 – 4 weeks and the theoretcial part of the syllabus covers the physics and physiology of closed bell diving, the use of mixed gases and the layout and design of systems.

The practical training covers transfers from bell to chamber, bell deployment and recovery, rescuing divers to and from the bell and culminates in the divers going into saturation and staying in the chamber for a period of 3 days.

Career Pathways

Bell Diver is the pinnacle of diver qualifications, however, with experience offshore, a bell diver may move into related or more advanced fields such as:

  • Life Support Technician
  • supervision
  • client representation
  • project management
  • diver training or diver training management

Supervisory roles are suitable for experienced and competent individuals and can range from Onshore Air Supervisor to Offshore Closed Bell Supervisor—all being responsible for ensuring safety and effectiveness in the work environment.

ADAS Diver Trainers (DTs) and ADAS Training and Assessment Managers (ATAMs) work from ADAS Accredited Training Establishments and are responsible for the delivery of training programs relevant to the qualification held by the trainer and the conduct of assessments in accordance with ADAS guidelines and requirements.

Thanks to The Underwater Centre Tasmania (TUCT) for contributing to this web page.

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