Diving using mixed gas rebreathers
Mixed gas rebreather dive qualifications
Rebreather diving equipment using mixed gases
Pre-dive checks and emergency procedures
Blending, testing and storage of mixed gases
Employers or self-employed people operating mixed gas rebreather diving should ensure that:
- mixed gas rebreather diving does not take place unless a dive supervisor is present at the site
- only a certificated mixed gas rebreather diver undertakes recreational diving using a mixed gas rebreather unless the diver is undertaking training for the purpose of certification as a mixed gas rebreather diver in accordance with this code
- maximum dive depth 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 whilst on a mandatory decompression stop
- nitrogen in the mixture being breathed at any time exceeds a partial pressure of 4.0 bar while diving
- oxygen partial pressure exposure times are not exceeded
- 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 rebreather dive safety log and on the cylinder
- mixed gas rebreathers should not be used for introductory experiences or resort dives in open water
- mixed gas rebreathers should be used only for divers in open water undergoing training for certification in mixed gas rebreather diving, or for divers who are already certificated to use a mixed gas rebreather.
Mixed gas rebreather dive qualifications
A mixed gas rebreather dive instructor should:
- be trained and certificated by a recreational technical diving training organisation to instruct in mixed gas rebreather diving
- be a certificated EANx instructor
- be qualified as a mixed gas rebreather diver for the model being used
- have completed 50 dives using a mixed gas rebreather and 20 dives with the rebreather model being used for instruction
- have successfully completed a rebreather instructor's course on the model being used.
Before a trainee undertakes a course in recreational diving using a rebreather and mixed gas, the trainee should:
- be certificated as an EANx scuba diver
- have a minimum of 100 logged dives, 20 of which must be with EANx
- before being granted certification, have completed at least one confined water session and eight open water dives using the rebreather during training.
Rebreather diving equipment using mixed gases
Equipment required for diving using mixed gas rebreathers includes:
- fins and mask
- mixed gas rebreather unit
- buoyancy control device
- two submersible depth gauges and two submersible timing devices or two dive computers
- cylinder pressure gauges connected to each cylinder used
- a redundant gas breathing system
- quick-release weight system and exposure protection
- a reel where direct ascent to the surface is not possible.
A more complete listing of equipment is available in section 3.2.4 of the Code of Practice for Recreational Technical Diving.
Pre-dive checks and emergency procedures
Divers should be advised about:
- the dive plan
- omitted decompression procedures
- emergency procedures including:
- loss of breathing gas procedures
- buddy separation 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.
The manufacturers' recommendations and/or specifications should be followed in respect of:
- pre-dive checks and emergency procedures
- carbon dioxide scrubbers.
Blending, testing and storage of mixed gases
Employers or self-employed people operating mixed gas rebreather diving should ensure that:
- all gas blending is undertaken by a competent person in the blending of gases to produce underwater breathing mixtures
- all equipment associated with the filling or use of mixed gases is to be used in accordance with manufacturers' recommendations
- all cylinders to be used for the storage of mixed gas are clearly marked as to their contents
- prior to using a mixed gas cylinder, the O2 content in the cylinder is tested by the diver
- after testing, a tag/decal is attached to the cylinder showing:
- oxygen percentage
- calculated nitrogen percentage
- calculated helium or other gas percentage
- minimum operating depth of the gas mixture
- maximum operating depth of the gas mixture
- cylinder serial number, in case the tag/decal is separated from the cylinder.
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