Diving using EANx

EANx (enriched air nitrox) is a breathing gas where the oxygen volume in the mixture is at least 22 per cent. It's breathed by divers in both open circuit SCUBA and rebreather equipment.

Generally using EANx reduces the diver's exposure to elevated partial pressures of nitrogen which reduce their risk of decompression illness. However elevated partial pressures of oxygen (PPO2) create serious toxic risks with both possible acute and chronic effects. Therefore depths and times of exposure to different EANx mixtures are limited.

Rebreathers are underwater breathing devices using a breathing circuit rather than an open system. The breathing quality of the air is maintained using chemical absorption to remove carbon dioxide while oxygen and diluent (air, EANx or other inert gases) are added. These systems use in line sensors and computers to monitor the breathing gas and alert the diver if required. The benefits of rebreathers include quietness, the ability to vary the breathing gas mix during the dive and efficient gas usage. The risks include the system flooding and failures in the use of the various components of the breathing circuit resulting in toxic or hypoxic breathing gas.

Diving using EANx with SCUBA

Diving using EANx therefore requires additional skills, equipment, procedures, training and supervision.

Persons conducting a business or undertaking (PCBU)  that involves diving on SCUBA with EANx should ensure:

• EANx diving does not take place unless an EANx dive supervisor is present at the dive site
• only a certificated EANx scuba diver undertakes recreational scuba diving using EANx unless the diver is undertaking:
  • training for the purpose of certification as an EANx scuba diver in accordance with this code
  • an introductory dive experience and the diver is accompanied by an EANx dive instructor
• PPO₂ exposure times are not exceeded
• maximum depth of a dive is based on the PPO₂ for the specific EANx breathing mixture used and does not exceed 1.6 bar PPO₂
• before a breathing mixture is used, the diver conducts a gas analysis to verify the oxygen content. The results should be recorded in the EANx dive safety log and on the cylinder.

Divers should be advised about:

• the dive plan
• the maximum depth for the breathing gas and loss of breathing gas procedures
• buddy separation procedures
• emergency procedures, including 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's.

Follow these links for information about EANx qualifications, equipment for EANx diving and the blending, testing, storage and use of EANx.

Diving using EANx rebreathers

The person conducting the business or undertaking should ensure:

• EANx rebreather diving does not take place unless, present at the dive site, is either an EANx rebreather dive supervisor, or an EANx dive supervisor who ensures each rebreather diver conducts the appropriate checks on their rebreather unit. The appropriate checks are:
  • check the rebreather unit scrubber is operational and not expired
  • check the unit's flow rate
  • test the mouthpiece check valves
  • checked by pass valve functions, if applicable
  • conduct a positive pressure test
  • conduct a negative pressure test
  • analyse the gas supply
  • check that the analyser is in test
  • check the redundant gas supply system is working
  • check the oxygen partial pressure monitor, if applicable.
• only a certificated EANx rebreather diver undertakes recreational diving using EANx rebreathers unless the diver is undertaking training for the purpose of certification as an EANx rebreather diver in accordance with the Recreational Diving, Recreational Technical Diving and Snorkelling Code of Practice 2018 (PDF, 0.61 MB)
• oxygen partial pressure exposure times are not exceeded
• maximum depth of a dive is based on the PPO₂ for the specific EANx breathing mixture used and does not exceed 1.6 bar PPO₂
• before a breathing mixture is used, the diver conducts a gas analysis to verify the O₂ content. The results should be recorded in the EANx Rebreather dive safety log and on the cylinder.
• rebreathers should not be used for introductory experiences or resort dives in open water for non-certificated diving.

Divers should be advised about:

• the dive plan
• dive objectives
• maximum depth for the breathing gas
• loss of breathing gas procedures
• buddy separation procedures
• safety requirements
• emergency procedures, including 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.
• manufacturer's pre-dive checks, emergency procedures and advice on carbon dioxide scrubbers.