ADAS Trimix (normoxic)

In response to the fact that tunneling projects are getting deeper, Pressureworx has developed an endorsement for the Hyperbaric Tunnel Workers course which is designed to train the workers in the safe procedure for using trimix breathing gas and equipment to a pressure of 6.6 bar (g).

Course Outline

To gain the qualification the worker must prove to be competent in both theory and practicable application.

Assessment is a combination of recognition of prior learning through entry prerequisites, and information and skills taught and assessed during course.

The topics covered include:

  1. Check and prepare the equipment for normoxic trimix tunneling intervention
  2. Participate in a tunneling intervention at depths that comply with local legislation using normoxic trimix
  3. Carry out post intervention equipment checks
  4. Identify and outline procedures used to operate a mixed gas system
  5. Identify and outline the hazards and risk controls associated with mixed gas systems


  • A current Workplace First Aid Certification
  • A current medical certificate to AS2299 or AS4774
  • A current OH&S Induction for Construction Work
  • A current site induction
  • Trade or construction qualifications or experience
  • Must have completed the Hyperbaric Tunnel Workers course

Any worker that that does not have the listed prerequisites will require additional training prior to certification

Assessment & Accreditation

The course includes a test compression between 50m and 70m (5 and 7 bar) using normoxic trimix. This can be completed in the medical lock or on the TBM however as most medical locks have a maximum operating pressure of 5 bar (g) this intervention is usually completed on the TBM. While the pressure of this intervention can be modified to meet local regulations it should be to at least the pressure expected on the project. The second intervention must be completed on the TBM using the TBM intervention equipment and must be completed using normoxic trimix. The pressure of the second intervention will be dictated by the tunneling conditions at the time.

Theory topics include legislation, risk assessment, TBM trimix breathing equipment details, cylinder marking and gas analysis, advantages and disadvantages of trimix, trimix physiology, decompression tables, and trimix tunnelling procedures. There will be a written examination to complete the assessment.

Additional information

The course is supported with a textbook specifically written for hyperbaric tunneling.

This course meets the training requirements set out by ADAS and successful candidates will be issued with a Trimix (normoxic) endorsement on their ADAS Hyprerbaric Tunnel Workers certification.