- What the Credential Actually Is
- Who Governs It and Where the Content Comes From
- The Prerequisite Ladder Before You Can Sit the Exam
- The Five Study Domains in Detail
- Section 3.6 Supervisor Responsibilities, Unpacked
- Exam Format, Fees and What Is Not Published
- Where the Card Gets Used
- Sequencing Your Preparation
- Frequently Asked Questions
- This credential is the ADCI HeO2/mixed-gas supervisor qualification, built on ADCI Consensus Standards edition 6.5.
- Eligibility requires at least 350 field days, 150 working dives, and 30 working days as an assistant mixed-gas supervisor.
- You must already be qualified as an air-diving supervisor before the mixed-gas supervisor card is possible.
- The issuer's certification page lists an online exam and $275 for the supervisor card category.
What the Credential Actually Is
The Mixed Gas Diving Supervisor credential is the qualification that lets an experienced diver or air-diving supervisor take formal control of surface-supplied helium-oxygen (HeO2) diving operations. It is not a general scuba certificate, and it is not an entry-level course. It sits near the top of the commercial diving career ladder, where the person holding the card is the one making go/no-go decisions, controlling gas supplies, and managing the emergency response when something goes wrong at depth.
In practical terms, the supervisor is the individual with immediate supervisory control of the dive. Under the ADCI standards, that means responsibility for the dive team, the life-support equipment, the dive plan, the gas profile, and the post-dive observation period. The card documents that an organization has vetted you, that you have the required field experience, and that you have passed the specific examination for this mode of diving.
If you want a wider orientation to the topic, the site also covers related definitions in What Is Mixed Gas Diving Supervisor Certification? and the broader Mixed Gas Diving Supervisor Certification overview.
Who Governs It and Where the Content Comes From
The governing body is the Association of Diving Contractors International (ADCI). The substantive material that candidates prepare from is the ADCI International Consensus Standards for Commercial Diving and Underwater Operations, currently published as edition 6.5 (the PDF revision filename carries a July 27, 2025 date). The issuer homepage links directly to this document, and the issuer's certification page describes the supervisor card categories and the online exam requirement.
An important point for anyone searching on this subject: several organizations in the diving world run supervisor-level examinations, and they are not interchangeable. This credential is the ADCI HeO2/mixed-gas supervisor examination. Preparing from materials written for a different body's supervisor exam, or assuming that a different certifying organization's syllabus maps onto this one, is a common and costly mistake. Your study source is the ADCI standards, and the sections that matter are specific.
The Prerequisite Ladder Before You Can Sit the Exam
This is not a credential you can reach by passing a course alone. The standards stack several requirements, and the exam is only one rung. A candidate needs all of the following:
- At least 350 field days as an air or mixed-gas diver.
- At least 150 working dives.
- At least 30 working days as an assistant mixed-gas supervisor.
- Prior qualification as an air-diving supervisor.
- Employer vetting and a written assignment to the supervisory role.
- A mode-specific supervisor card for mixed-gas diving.
- Medical fitness before any hyperbaric exposure.
- Valid CPR and first aid credentials.
The 30 working days as an assistant mixed-gas supervisor deserve special attention. That requirement means your employer has to put you in a position to shadow and assist a working mixed-gas supervisor, which in turn means the credential is as much about your employment relationship as your personal study. For a deeper walk through eligibility, see Mixed Gas Diving Supervisor Requirements: Eligibility, Prerequisites & How to Qualify.
| Requirement | What the standards call for |
|---|---|
| Field experience | At least 350 days as an air or mixed-gas diver |
| Working dives | At least 150 |
| Assistant supervisor time | At least 30 working days as assistant mixed-gas supervisor |
| Prior supervisory qualification | Qualified air-diving supervisor |
| Employer role | Vetting plus written assignment |
| Medical and safety | Medical fitness before hyperbaric exposure; valid CPR/first aid |
| Examination | The specific ADCI HeO2/mixed-gas supervisor exam |
The Five Study Domains in Detail
The preparation map used on this site breaks the source material into five groupings. Each corresponds to identifiable sections of the ADCI standards. For a full treatment of each area, see Mixed Gas Diving Supervisor Exam Domains: Complete Guide to All 5 Content Areas. Here is what each one asks of you.
Domain 1: HeO2/Mixed-Gas Diving Supervisor Responsibilities, Qualifications and Certification
This grouping centers on section 3.6 of the standards, which covers supervisor duties, qualifications and card requirements.
- The full list of supervisory responsibilities (detailed in the next section)
- Qualification pathway: experience thresholds, air-supervisor prerequisite, mode-specific card
- Employer vetting and written assignment mechanics
- Medical fitness, CPR and first aid requirements
Domain 2: Surface-Supplied Mixed-Gas Diving (HeO2)
This grouping draws on section 4.4, which covers operational personnel and equipment requirements for surface-supplied mixed-gas diving.
- Personnel requirements for a mixed-gas dive team
- Equipment requirements specific to HeO2 operations
- Dress and emergency gas arrangements
- How mixed-gas operations differ from air diving in staffing and gear
Domain 3: Underwater Operations: Procedures, Checklists and Guidelines
Drawing on the operations material in section 5, this grouping is about how a dive is actually run.
- Pre-dive and post-dive checks and checklists
- Job safety analysis and dive planning
- Team briefings and operation-specific procedures
- Depth, time and gas profiles, plus continuous tending and termination criteria
Domain 4: Life-Support Equipment: Requirements, Maintenance and Testing
Drawing on the equipment material in section 6, this grouping is the hardware side of the job.
- Helmets and masks, hoses and umbilicals
- Compressors and air purity, manifolds and regulators
- Launch and recovery systems, entry and egress
- Gauges and timekeeping, compressed-gas equipment, and pressure vessels for human occupancy
- Maintenance, inspection and testing requirements
Domain 5: Emergency Procedures, Assessments and Reporting of Accidents
Drawing on the emergency preparation material in section 7, this grouping tests whether you can respond when the plan fails.
- Loss of breathing media or communications
- Trapped or injured diver scenarios
- Umbilical damage, fire and equipment failure
- Adverse conditions and incident reporting
Section 3.6 Supervisor Responsibilities, Unpacked
Because Domain 1 is the most directly "you" part of the exam, it is worth reading the section 3.6 responsibility list as a working job description. Grouped by function, the standard expects a mixed-gas supervisor to handle the following.
Compliance and control
- Ensure compliance with regulations and the employer's own manuals.
- Maintain immediate supervisory control of the dive.
- Coordinate with vessels and sites, and operate from a suitable surface location.
Planning and briefing
- Conduct job safety analysis and dive planning, including gas supplies.
- Brief the team and apply operation-specific procedures.
- Establish depth, time and gas profiles.
- Keep current manuals, decompression information and treatment information on hand.
People and equipment
- Verify team duties and fitness for work.
- Confirm life-support equipment is suitable, compliant and inspected.
- Perform pre-dive and post-dive checks.
Execution and emergencies
- Ensure continuous tending of the diver.
- Apply termination criteria when conditions require.
- Maintain emergency and medical communications.
- Observe the diver after the dive for symptoms.
- Confirm chamber availability and post-treatment arrangements.
Records
- Complete incident reports, maintain records and verify logs.
Notice how many items are about preparation and documentation rather than in-water action. Candidates who come from a strong hands-on diving background sometimes underweight the planning and record-keeping items, and those are exactly the kind of details a standards-based exam can test.
Exam Format, Fees and What Is Not Published
Here is where it pays to be careful about what is actually known. The issuer's current certification page lists an online exam as required and shows $275 for the supervisor card category. That figure should be understood as the card-category amount listed by the issuer, not as an independently verified exam-only fee. If you are budgeting, confirm the current fee structure directly with ADCI, and read the fuller discussion in Mixed Gas Diving Supervisor Certification Cost: Complete Pricing Breakdown.
What is not established in the public sources: the number of questions, the time limit, the passing score, a pass rate, and any official table of exam weights. Anyone quoting precise figures for these is either guessing or drawing on a different credential. For that reason, the site's pages on passing score and pass rate are written around that uncertainty rather than inventing numbers.
| Item | Status |
|---|---|
| Governing body | Association of Diving Contractors International |
| Source document | ADCI Consensus Standards edition 6.5 |
| Exam delivery | Online exam listed as required by the issuer |
| Supervisor card category fee listed | $275 (card category, not a verified exam-only fee) |
| Question count | Not established |
| Time limit | Not established |
| Passing score | Not established |
| Pass rate | Not established |
| Official domain weights | Not established |
Key Takeaway
Because the exam's structure is not publicly detailed, your safest preparation strategy is to know the source standards deeply rather than to optimize for an assumed question format. Mastery of sections 3.6, 4.4, 5, 6 and 7 is the dependable path.
Where the Card Gets Used
The mixed-gas supervisor card matters most to commercial diving contractors who run surface-supplied HeO2 operations, particularly deeper work where air is no longer suitable. The credential requires employer vetting and a written assignment, so in practice the people who hold it are either already employed by a diving contractor or being developed internally for supervisory roles. Because the standards expect 30 working days as an assistant supervisor, the typical route is an internal progression: diver, air-diving supervisor, assistant mixed-gas supervisor, then mixed-gas supervisor.
That also means the card is as much a statement about trust as skill. A contractor assigning you in writing to supervise a mixed-gas dive is accepting responsibility for your decisions. For a look at the roles available, see Mixed Gas Diving Supervisor Jobs, and for the financial angle, Mixed Gas Diving Supervisor Salary Guide and Is the Mixed Gas Diving Supervisor Certification Worth It?. Those pages avoid quoting unsupported figures and discuss the value qualitatively.
Sequencing Your Preparation
Rather than a generic study schedule, order your work by how the domains depend on each other. Domain 1 comes first because it defines the role and frames everything else. Domain 4 and Domain 2 come next because equipment and personnel requirements are the vocabulary you need before operations make sense. Operations and emergencies come last because they apply everything that came before.
Domain 1: Role and Qualifications
- Read section 3.6 end to end and rewrite each responsibility in your own words
- Memorize the 350 / 150 / 30 experience thresholds and the prerequisite chain
Domains 2 and 4: Personnel and Equipment
- Work through section 4.4 and the equipment sections on helmets, umbilicals, compressors, manifolds and pressure vessels
- List maintenance and testing items for each equipment type
Domain 3: Operations
- Study checklists, job safety analysis, dive planning and gas profile requirements
- Practice articulating termination criteria
Domain 5: Emergencies and Review
- Walk through each emergency scenario as the supervisor
- Take timed practice questions on the practice test site and revisit weak sections
For a fuller plan, see the Mixed Gas Diving Supervisor Study Guide, and when you want a quick refresher close to the exam, the Mixed Gas Diving Supervisor Cheat Sheet condenses the must-know facts. If you are weighing how demanding the process is, How Hard Is the Mixed Gas Diving Supervisor Exam? gives a balanced perspective. When you are ready to test yourself, you can start with the free questions at the Mixed Gas Diving Supervisor Exam Prep home page.
Frequently Asked Questions
It qualifies you to act as the supervisor with immediate control of surface-supplied HeO2/mixed-gas dives under the ADCI standards, covering planning, equipment, team management, emergencies and record verification.
The Association of Diving Contractors International (ADCI). Preparation is based on the ADCI International Consensus Standards, currently edition 6.5, not on examinations from other organizations.
The standards call for at least 350 field days as an air or mixed-gas diver, 150 working dives, and 30 working days as an assistant mixed-gas supervisor, plus prior air-diving supervisor qualification and employer vetting with a written assignment.
The issuer's certification page lists an online exam as required and $275 for the supervisor card category. That is not an independently verified exam-only fee, so confirm current amounts with ADCI before budgeting.
Those details are not established in the public sources. The question count, time limit, passing score, pass rate and an official weighting table are all unpublished, so focus on mastering the source standards rather than relying on assumed numbers.