Mixed Gas Diving Supervisor Requirements 2026: Eligibility, Prerequisites & How to Qualify

What This Credential Actually Is

The Mixed Gas Diving Supervisor credential discussed here is the supervisor qualification governed by the Association of Diving Contractors International (ADCI). It is built around the ADCI International Consensus Standards, currently edition 6.5, and it authorizes a qualified individual to supervise surface-supplied helium-oxygen (HeO2) mixed-gas diving operations.

That distinction matters. Other organizations run their own diving supervisor schemes, and those schemes have different prerequisites, examinations and card systems. Nothing in this article applies to ADC-UK or IMCA examinations. If you are planning a career around ADCI-governed work, the requirements below are the ones that count.

If you are still orienting yourself on the basics, our overview What Is A Mixed Gas Diving Supervisor? covers the role itself, while this guide stays focused on who qualifies and how.

The Requirements at a Glance

The qualification is a stack of requirements, and every layer has to be in place. Passing the examination alone does not make you a mixed-gas supervisor.

The Experience Ladder: Days, Dives and Assistant Time

350 field days as an air or mixed-gas diver

The standards require at least 350 field days working as an air or mixed-gas diver. The wording matters: the days can be accumulated in either air or mixed-gas diving, which reflects how most commercial divers progress. A field day is working time in the operating environment, so documentation from your employers is the cleanest way to substantiate it.

150 working dives

Separately from field days, the standards require at least 150 working dives. These are two distinct counts. A diver could accumulate many field days with relatively few dives on a long standby-heavy project, or many dives in fewer days on a busy inspection campaign. You need to satisfy both thresholds, so track them independently in your logbook rather than assuming one implies the other.

30 working days as assistant mixed-gas supervisor

The apprenticeship step is 30 working days as an assistant mixed-gas supervisor. This is where you stop being the person in the water and start learning to run the operation from the surface: watching how the supervisor manages gas supplies, monitors the dive profile, tends the diver, and communicates with the vessel or site. Because these days count toward qualification, they are worth seeking out deliberately. Ask your employer early how assistant-supervisor time is assigned and recorded.

Why Air-Diving Supervisor Qualification Comes First

The standards require that a mixed-gas supervisor already be qualified as an air-diving supervisor. In practical terms, this means the mixed-gas credential is a second tier. You are expected to have already demonstrated command of surface-supplied diving supervision before taking on HeO2 operations, where decompression obligations, gas management and emergency options become more demanding.

This prerequisite shapes career planning. Divers aiming at mixed-gas supervision should not skip the air-supervisor step or treat it as a formality. The knowledge carries directly into mixed-gas work: dive planning, equipment checks, communications, tending, and incident reporting are all themes you will meet again, with additional mixed-gas layers on top.

For a broader view of what the credential involves once you reach it, see our page on Mixed Gas Diving Supervisor Certification.

Employer Vetting and Written Assignment

One of the more unusual aspects of this credential is that your employer is part of the qualification chain. The standards call for employer vetting and a written assignment to supervise. In other words, holding a card does not by itself entitle you to supervise on any job; the employer must assess your competence and formally assign you to the role in writing.

This ties directly to the supervisor responsibilities in Section 3.6 of the standards, which include compliance with regulations and the employer's own manuals. A supervisor works inside a company's procedures, so the assignment process reflects that the employer carries responsibility for who is placed in charge of a dive.

• Practical implication: build a track record your employer can vouch for, because their vetting is a gate you cannot study your way around.
• Documentation habit: keep a copy of any written assignment, since it is evidence of your authorized scope.
• Job changes: expect a new employer to run its own vetting rather than simply accepting your previous assignment.

Medical Fitness, CPR and First Aid

Two baseline requirements sit alongside the experience thresholds. First, medical fitness before hyperbaric exposure: you must be medically fit to dive before being exposed to pressure. Second, current CPR and first aid certification must be valid.

These are easy to overlook because they feel administrative, but they are active requirements. A lapsed CPR certificate or an expired medical can interrupt your eligibility regardless of how complete your logbook is. Set calendar reminders for renewal dates well in advance, particularly if your work rotation makes last-minute training difficult to schedule.

The Supervisor Card and the Examination

A mode-specific card

The standards require a mode-specific supervisor card. That means the card reflects the diving mode you are qualified to supervise, and a mixed-gas card is distinct from an air-diving supervisor card. The two-tier structure described above is reflected directly in the cards themselves.

The examination and registration

The credential requires passing the specific ADCI HeO2/mixed-gas supervisor examination. The current ADCI certification page lists an online exam as required and shows $275 for the supervisor card category. Be careful how you interpret that figure: it is the listed fee for the card category, and it should not be read as an independently verified exam-only fee. Check the ADCI certification page directly for current registration steps and pricing before you budget. Our breakdown of Mixed Gas Diving Supervisor certification cost goes into how to think about the full spend, including training and recertification-related costs beyond the card fee.

Several exam logistics are not established in the source material: the number of questions, the time limit, the passing score, the pass rate, and any official weighting table. Anyone quoting precise figures for those should be treated with skepticism. For context on how to think about what is and is not known, see Mixed Gas Diving Supervisor Passing Score and Mixed Gas Diving Supervisor Pass Rate.

What the Exam Will Expect You to Know

The examination content is drawn from ADCI Consensus Standards edition 6.5. Our preparation framework groups the relevant material into five study areas. These are editorial groupings built from published standards sections, not an official exam blueprint with published weights, so treat them as a study map rather than a statement of exam proportions.

For a deeper walk through each area, read Mixed Gas Diving Supervisor Exam Domains: Complete Guide to All 5 Content Areas. To see how this content translates into question practice, the Mixed Gas Diving Supervisor practice tests are built around these same study groupings.

A Realistic Path From Diver to Supervisor

Because the requirements stack, the order of operations matters more than speed. The following progression reflects how the prerequisites naturally build on one another.

1. Build diving experience. Accumulate field days and working dives while keeping meticulous, verifiable records.
2. Qualify as an air-diving supervisor. This is a hard prerequisite for the mixed-gas tier.
3. Gain mixed-gas exposure. Seek roles on HeO2 operations so the 350 field-day total and the assistant-supervisor time have somewhere to come from.
4. Complete 30 working days as assistant mixed-gas supervisor. Treat this as a structured apprenticeship, not time served.
5. Secure employer vetting and written assignment. Confirm your employer's process well before you need it.
6. Keep medical, CPR and first aid current. Verify expiry dates against your planned exam and assignment timeline.
7. Prepare for and pass the ADCI HeO2/mixed-gas supervisor examination, then obtain the mode-specific supervisor card.

Timing your exam preparation

One piece of scheduling logic is worth applying: study Domain 1 first, because Section 3.6 frames how you read everything else, then move to Domains 2 and 4 together since equipment and surface-supplied operations reinforce each other. Leave Domain 5 for later passes, when emergency scenarios can draw on everything you have already covered. Our Mixed Gas Diving Supervisor Study Guide lays out a fuller plan, and the exam dates and scheduling guide explains how to think about timing.

Qualification Pitfalls to Avoid

If you are weighing whether the investment of time and money is justified, Is the Mixed Gas Diving Supervisor Certification Worth It? examines the trade-offs, and How Hard Is the Mixed Gas Diving Supervisor Exam? gives a candid view of the exam itself.

Frequently Asked Questions

Qualifying as a mixed-gas diving supervisor is a long-horizon project that rewards careful record-keeping and early planning. When you are ready to test your command of the standards, the Mixed Gas Diving Supervisor practice exam is a practical place to start.