Diving using mixed gas rebreathers

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.

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.

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:

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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