Diving using mixed gas with SCUBA
Mixed gas dive qualifications
Equipment for mixed gas diving
Pre-dive checks and emergency procedures
Employers or self-employed people should ensure:
- mixed gas diving does not take place unless a dive supervisor is present at the dive site
- only a certificated mixed gas scuba diver undertakes recreational scuba diving using mixed gases unless the diver is undertaking training for the purpose of certification as a mixed gas scuba diver in accordance with this code
- oxygen partial pressure exposure times are not exceeded
- maximum depth of a dive does not exceed the depth where:
- oxygen in the mixture being breathed at any time exceeds a partial pressure of 1.4 bar while diving and 1.6 bar during decompression
- nitrogen in the mixture being breathed at any time exceeds a partial pressure of 4.0 bar while diving
- minimum depth does not exceed the depth where oxygen in the mixture currently being breathed is less than a partial pressure of 0.16 bar
- before a breathing mixture is used, the diver conducts a gas analysis to verify the oxygen content. The results should be recorded in the mixed gas dive safety log and on the cylinder.
Mixed gas dive qualifications
A mixed gas dive instructor should:
- be trained and certificated by a recreational technical diving training organisation to instruct in mixed gas diving
- be trained and certificated by a recreational technical diving training organisation to instruct in decompression diving
- be a certificated EANx instructor
- have instructed and certificated at least 25 EANx divers
- be qualified as a mixed gas diver
- have completed 15 mixed gas dives.
Before a trainee undertakes a course in recreational scuba diving using mixed gas, the trainee should:
- be a certificated EANx scuba diver
- be a certificated decompression diver
- have a minimum of 150 logged dives, of which 50 have been at a depth greater than 30 metres
- have completed a minimum of 30 logged dives within the last 12 months
- have completed a minimum of 30 dives using EANx.
Equipment for mixed gas diving
Equipment for mixed gas diving includes:
- fins and mask
- compressed gas cylinders and valves designed specifically for SCUBA
- buoyancy control device
- regulators are on all cylinders
- two submersible depth gauges and two submersible timing devices, or two dive computers
- a redundant gas breathing system
- two copies of the dive team's dive plan
- whenever cylinders are manifolded, an isolation valve should be fitted to the manifold
- alternative ascent system.
A more complete listing of equipment can be found in section 3.1.4 of the Code of Practice for Recreational Technical Diving.
Pre-dive checks and emergency procedures
Divers should be advised about:
- the dive plan and gas change over depths
- the sequence and role of each diver
- gas turn around pressures and analysing gas mixtures
- maximum and minimum depths for each breathing gas and run times
- omitted decompression procedures
- analysing their gas mixture
- emergency procedures including:
- loss of breathing gas procedures
- buddy separation procedures
- loss of ascent path procedures
- the location of and contact procedures for the nearest recompression facilities
- checking the position and correct operation of their own equipment and that of their buddy
- performing for themselves and their buddy an in-water check (leak test) and an in-water regulator location and correct operation check.
More information on mixed gas diving is available in section 3 of the Code of Practice for Recreational Technical Diving.
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