- What the Credential Actually Is
- Who Governs It and What the Standards Say
- The Experience and Qualification Ladder
- The Five Content Areas You Study
- What Section 3.6 Expects of a Supervisor
- Equipment and Emergency Topics Candidates Must Master
- Exam, Card and Fee Mechanics
- What Is Not Published
- Where the Credential Matters
- Sequencing Your Preparation
- Frequently Asked Questions
- This credential is the ADCI HeO2/mixed-gas supervisor qualification, built on Consensus Standards edition 6.5, not an ADC-UK or IMCA scheme.
- Eligibility requires 350 field days, 150 working dives and 30 working days as assistant mixed-gas supervisor.
- Air-diving supervisor qualification, employer vetting, medical fitness and valid CPR/first aid are also required.
- ADCI's certification page lists an online exam and $275 for the supervisor card category.
What the Credential Actually Is
The Mixed Gas Diving Supervisor certification is the qualification that authorizes a person to supervise surface-supplied helium-oxygen (HeO2) diving operations under the Association of Diving Contractors International (ADCI) system. It is not an entry-level diving card and it is not a general "supervisor" certificate. It is a mode-specific supervisor credential: the person who holds it is the individual accountable on the surface for the safety of divers breathing mixed gas, from planning through decompression and post-dive observation.
If you have seen the same phrase used elsewhere, be careful. This article is strictly about the ADCI HeO2/mixed-gas supervisor pathway. It does not describe examinations run by ADC-UK, IMCA or any other body, and the experience thresholds, card mechanics and study material discussed here belong to the ADCI framework only. For a shorter orientation to the term itself, see What Is Mixed Gas Diving Supervisor? and What Does Mixed Gas Diving Supervisor Stand For?
Who Governs It and What the Standards Say
The governing body is the Association of Diving Contractors International. The framework behind the credential is the ADCI International Consensus Standards, and the edition linked from the issuer homepage at the time of writing is edition 6.5 (the PDF revision filename is dated July 27, 2025). Candidates should always confirm which edition is current before they begin studying, because the standards are revised and your preparation should match the version your examination draws from.
Several sections of the standards matter most for this credential:
- Section 3.6 covers mixed-gas supervisor duties, qualifications and card requirements.
- Section 4.4 covers surface-supplied mixed-gas operational personnel and equipment requirements.
- Sections 5, 6 and 7 supply the operations, equipment and emergency preparation material that supervisors must apply.
For a deeper walk through each grouping, read Mixed Gas Diving Supervisor Exam Domains 2026: Complete Guide to All 5 Content Areas.
The Experience and Qualification Ladder
This is not a credential you can sit for early. The ADCI pathway layers experience, prior qualification and administrative sign-off before a mixed-gas supervisor card is issued. The documented requirements are:
| Requirement | What the standards and issuer information specify |
|---|---|
| Field experience | At least 350 field days as an air or mixed-gas diver |
| Working dives | At least 150 working dives |
| Supervisory apprenticeship | At least 30 working days as assistant mixed-gas supervisor |
| Prior supervisor status | Qualification as an air-diving supervisor |
| Employer role | Employer vetting and a written assignment |
| Card type | A mode-specific supervisor card |
| Medical | Medical fitness before any hyperbaric exposure |
| Safety training | Valid CPR/first aid |
| Examination | Passing the specific ADCI HeO2/mixed-gas supervisor examination |
Notice what this implies. The assistant-supervisor requirement means you are expected to have watched, and participated in, real mixed-gas supervision before you hold the card yourself. The air-diving supervisor prerequisite means the mixed-gas credential sits on top of an existing supervisory foundation rather than replacing it. For a complete eligibility walkthrough, see Mixed Gas Diving Supervisor Requirements 2026: Eligibility, Prerequisites & How to Qualify.
The Five Content Areas You Study
This site organizes preparation into five groupings that map to the published standards. They are editorial study aids, but they reflect where the supervisor's responsibilities genuinely live.
Domain 1: HeO2/Mixed-Gas Diving Supervisor Responsibilities, Qualifications and Certification
This area is anchored in section 3.6. Candidates must know who may supervise, what the card requires, and what the supervisor is personally responsible for.
- Qualification and card requirements
- Compliance with regulations and the employer's manual
- Records, logs and incident reporting duties
Domain 2: Surface-Supplied Mixed-Gas Diving (HeO2)
This area focuses on the mixed-gas mode itself and the personnel and equipment the standards require for it, drawing on section 4.4.
- Operational personnel requirements
- Gas supply planning for the dive
- Mixed-gas context rather than air-diving defaults
Domain 3: Underwater Operations: Procedures, Checklists and Guidelines
Here the focus is on running the dive: briefings, checks, profiles and termination decisions.
- Pre-dive and post-dive checks
- Depth, time and gas profiles
- Operation-specific procedures and continuous tending
Domain 4: Life-Support Equipment: Requirements, Maintenance and Testing
This grouping covers the hardware that keeps divers alive and the discipline of keeping it inspected and documented.
- Dress, helmets, masks and emergency gas
- Umbilicals, manifolds, regulators and compressors
- Maintenance and testing records
Domain 5: Emergency Procedures, Assessments and Reporting of Accidents
The supervisor is the person who must respond when something goes wrong, then document it accurately.
- Loss of breathing media or communications
- Trapped or injured diver, umbilical damage, fire
- Incident reporting and verification of logs
What Section 3.6 Expects of a Supervisor
Section 3.6 is the single most important reading for this credential, because it describes the supervisor's job in concrete terms. Rather than memorizing it as a list, group the responsibilities into the phases of a dive.
Before the dive
- Ensuring compliance with regulations and the employer's manual
- Confirming life-support equipment is suitable, compliant and inspected
- Completing job safety analysis and dive planning, including gas supplies
- Verifying team duties and team fitness
- Holding team briefings and confirming operation-specific procedures
- Ensuring current manuals, decompression tables and treatment information are on hand
- Coordinating with vessels or sites and selecting a suitable surface location
During the dive
- Maintaining immediate supervisory control
- Keeping to the planned depth, time and gas profiles
- Tending the diver continuously
- Maintaining emergency and medical communications
- Applying termination criteria when conditions require it
After the dive
- Completing post-dive checks
- Observing the diver for symptoms after the dive
- Confirming chamber availability and post-treatment arrangements
- Producing incident reports, maintaining records and verifying logs
Key Takeaway
Section 3.6 reads as a chain of accountability: plan, control, terminate, observe, document. When you study, ask of every duty which phase it belongs to and what evidence the supervisor must leave behind.
Equipment and Emergency Topics Candidates Must Master
Beyond section 3.6, the equipment and emergency material is where supervisors earn their credibility. The standards cover a broad hardware list, and a supervisor has to understand both what each item is for and how it is maintained and tested.
- Dress and emergency gas
- Helmets and masks
- Hoses and umbilicals
- Compressors and air purity
- Manifolds and regulators
- Launch and recovery, and entry and egress
- Gauges and timekeeping
- Compressed-gas equipment
- Pressure vessels for human occupancy
- Relevant maintenance and testing
On the emergency side, the standards address loss of breathing media or communications, a trapped or injured diver, umbilical damage, fire, equipment failure and adverse conditions. The right way to learn these is to rehearse them as decision sequences: what the supervisor recognizes, what is ordered, who is notified, and what gets written down afterward.
If you want a condensed pass through these facts once you have read the standards, the Mixed Gas Diving Supervisor Cheat Sheet 2026: One-Page Review of Must-Know Facts is a useful companion.
Exam, Card and Fee Mechanics
The credential requires passing the specific ADCI HeO2/mixed-gas supervisor examination. ADCI's current certification page lists an online exam as required and shows $275 for the supervisor card category. That figure should be read as the card-category listing on the issuer's page, not as an independently verified exam-only fee. Costs beyond that, such as medicals, training, travel and first aid or CPR renewal, vary by individual and are not covered by that listing. Verify the current amount directly with ADCI before budgeting.
For a broader look at what the path costs in practice, see Mixed Gas Diving Supervisor Certification Cost 2026: Complete Pricing Breakdown.
What Is Not Published
Honest preparation means knowing what you cannot know. The following details are not established in the sources this site relies on:
- The number of questions on the examination
- The time limit
- The passing score
- Any pass rate
- An official table of exam weights by domain
Because of this, be skeptical of anyone quoting precise numbers for these items. The practical response is to prepare against the source documents rather than against a rumored format. Our articles on passing score and pass rate discuss how to think about these gaps responsibly, and How Hard Is the Mixed Gas Diving Supervisor Exam? covers difficulty in qualitative terms.
Where the Credential Matters
The mixed-gas supervisor card is relevant to commercial diving contractors that conduct surface-supplied HeO2 work, and the standards themselves make employer vetting and written assignment part of the process. In other words, the credential does not float free of a job: an employer assigns the role in writing. That makes it most meaningful for working divers and assistant supervisors who already operate inside contractor organizations and are moving toward supervisory responsibility.
We do not quote salary figures here because none are established in the source facts for this credential. If you are weighing the career side, read Mixed Gas Diving Supervisor Jobs, Mixed Gas Diving Supervisor Salary Guide 2026 and Is the Mixed Gas Diving Supervisor Certification Worth It? for a qualitative treatment.
Sequencing Your Preparation
Because the material is a structured set of standards rather than a pool of trivia, it pays to read in the order the job itself unfolds. One sensible sequence:
Domain 1 foundations
- Read section 3.6 end to end and sort each duty into before, during and after the dive
- Note the card, vetting and assignment requirements
Domains 2 and 3
- Work through section 4.4 personnel and equipment requirements
- Review operations material: checklists, profiles, termination criteria
Domain 4 equipment
- Study each equipment category and its maintenance and testing expectations
- Pay attention to emergency gas and air purity
Domain 5 and review
- Rehearse emergency scenarios as decision sequences
- Take timed practice questions and revisit weak areas
Section 3.6 comes first because it frames everything else: once you know what the supervisor must verify, the equipment and emergency sections make more sense as supporting detail. For a fuller plan, see the Mixed Gas Diving Supervisor Study Guide 2026: How to Pass on Your First Attempt, and when you are ready to test recall, try the Mixed Gas Diving Supervisor practice tests. Timing questions are addressed in Mixed Gas Diving Supervisor Exam Dates 2026.
Frequently Asked Questions
The Association of Diving Contractors International administers it. It is tied to the ADCI HeO2/mixed-gas supervisor examination and the ADCI International Consensus Standards, currently edition 6.5. It is not an ADC-UK or IMCA credential.
The standards call for at least 350 field days as an air or mixed-gas diver, 150 working dives and 30 working days as assistant mixed-gas supervisor. You also need air-diving supervisor qualification, employer vetting with written assignment, medical fitness and valid CPR/first aid.
ADCI's certification page lists $275 for the supervisor card category and lists an online exam as required. That should not be read as an independently verified exam-only fee, so confirm current amounts with ADCI before you plan your budget.
Question count, time limit, passing score and pass rate are not established in the published sources. Prepare from the standards, especially sections 3.6, 4.4, 5, 6 and 7, rather than relying on unverified figures.
No. They are an editorial map of the published standards, created to make study manageable. They are not an official weighted blueprint, so treat them as a reading guide and not a guarantee of exam coverage.
For a related overview, see Mixed Gas Diving Supervisor Certification and Mixed Gas Diving Supervisor Training, and return to the main practice test site whenever you want to check your recall against exam-style questions.