CHRN Certification

What the CHRN Credential Actually Is

The Certified Hyperbaric Registered Nurse credential is the nursing-specific certification for registered nurses who care for patients receiving hyperbaric oxygen therapy (HBOT). It signals that a nurse can do more than operate a chamber. The nurse has demonstrated command of pressure physics, gas physiology, decompression theory, indications for hyperbaric oxygen, oxygen toxicity, barotrauma prevention, chamber safety, and the nursing process applied to patients under pressure.

If you are new to the acronym and want the plain-language basics first, our explainers on what CHRN is and what CHRN stands for cover the definition. This article focuses on how the certification works in practice: who governs it, what it demands before you can sit for the exam, what the exam looks like, and how to prepare for the actual content.

Who Runs It: BNACB and NBDHMT

Two bodies share responsibility for the CHRN. The Baromedical Nurses Association Certification Board (BNACB) oversees nursing eligibility and certification. The National Board of Diving and Hyperbaric Medical Technology (NBDHMT) administers and grades the examination at approved testing centers.

That split matters when you are troubleshooting logistics. Questions about whether your experience qualifies, or about preceptor and employer documentation, sit on the nursing-certification side. Questions about testing sites, scheduling, and score reporting run through the NBDHMT. The exam is not a default at-home, unproctored test. Online delivery is described as taking place at a designated testing site, and any in-house proctorship requires NBDHMT approval.

One terminology trap worth knowing: in NBDHMT materials, "CHT" refers to Certified Hyperbaric Technologist, the companion credential for non-nurse chamber staff. It is not related to any hospitality-trainer credential. The CHRN is also distinct from advanced or administrative pathways; this article targets the basic CHRN only.

The Eligibility Path, Step by Step

The CHRN is not an entry-level exam you can take straight out of nursing school. Eligibility is built around licensure, clinical background, and documented hands-on hyperbaric experience. For the full checklist, see our CHRN requirements guide; here is the structure at a glance.

1. Unrestricted RN license. A restricted or encumbered license is a problem at the outset.
2. General nursing experience. Two years in a hospital or clinic setting, or one year in critical care.
3. Recent active hyperbaric practice. Roughly the most recent year of active work in hyperbaric medicine.
4. Approved introductory training. A 40-hour introductory course, or applicable Category A credits that replace it.
5. Post-course patient care. 480 hours of direct patient care after the course.
6. Validation. Approval from a qualified preceptor and a recommendation from your employer.

Because the 480 hours follow the course, the practical timeline is front-loaded: you need real chamber time under a preceptor before the application is complete. If you are still choosing a course, our CHRN training overview explains what to look for.

Exam Format and Test-Day Rules

The examination is straightforward in structure, which is part of why the content, not the format, is the hard part.

Two hours for 120 items works out to a minute per question, which is comfortable for recall items but tight for multi-step pressure conversions and decompression table lookups. Practice those calculation-heavy items under timed conditions. For a deeper look at the cutoff itself, see what the CHRN passing score means.

On difficulty and pass rates, be careful with the numbers you see online. A current CHRN-specific pass rate is not publicly disclosed, and a historical 74% figure belongs to a combined program rather than the CHRN alone. We discuss what can and cannot be concluded in our CHRN pass rate analysis and in how hard the CHRN exam is.

Fees and Registration Mechanics

The current-linked June 2026 initial application confirms a three-tier fee structure based on membership, and it requires evidence of that membership.

The application says to register 30 days before the test, so treat that as a hard planning constraint rather than a suggestion. The June 2024 manual lists US$100 for a repeat examination; no newer retake-fee override turned up in the retrieved initial application, so confirm the current retake amount with the NBDHMT before budgeting for a second attempt.

Notice how much the fee varies by affiliation: a nonmember pays more than the BNA-member rate, so the cost of membership should be weighed against the exam-fee difference. Our CHRN certification cost breakdown adds the course fee, renewal, and membership into a full picture, and the CHRN exam dates guide covers scheduling windows.

What the Exam Covers: The Sixteen Content Areas

The June 2024 CHRN Resource Manual lists sixteen technical preparation topics in its study-guide contents. These are issuer study-guide competencies, not an officially weighted blueprint. A full current weighted blueprint, and therefore the largest-weighted domain, remains unverified, so do not trust anyone who gives you precise percentages per area. (The manual's introduction mentions twelve sections and its body contains thirteen detailed sections; neither count is an authenticated domain count.)

The sixteen areas are:

1. History of Undersea and Hyperbaric Medicine
2. The Physical Aspects of Undersea and Hyperbaric Medicine
3. The Physiological Aspects of Undersea and Hyperbaric Medicine
4. Mechanisms and Theory of Decompression
5. Therapeutic Mechanisms Associated with Hyperbaric Oxygen Exposure
6. Currently Accepted Indications for Hyperbaric Oxygen Exposure
7. Oxygen Toxicity
8. Other Potential Complications
9. The Hyperbaric Medicine Facility
10. Hyperbaric Safety I: Protecting the Environment
11. Hyperbaric Safety II: Protecting the Patient
12. Understanding of the NFPA guidelines for hyperbaric chambers
13. Transcutaneous Oxygen Monitoring
14. Nursing Management of the Patient Undergoing Hyperbaric Oxygen Therapy
15. Nursing Standards of Practice (BNA Hyperbaric Nursing Standards)
16. Understanding of basic operation of all hyperbaric chambers, including monoplace and multiplace chambers

For a domain-by-domain treatment, see our complete CHRN exam domains guide. Three of these entries (NFPA guidance, BNA standards of practice, and chamber operation) have no separate detailed chapter body in the manual, so you must pull their content from the external standards themselves and verify against current versions.

Where Candidates Struggle: Physics, Gas Laws and Decompression

Nurses are usually strong on assessment and patient care, and weaker on the physical sciences. The Physical Aspects objective is explicit about what you must be able to do, and most of it is calculation.

Because a pocket calculator is allowed, memorizing arithmetic is less important than knowing which formula to use and which units to feed it. A common failure point is mixing gauge and absolute pressure, so drill the distinction until it is automatic. Boyle's Law ties directly to barotrauma, Henry's Law to dissolved gas and decompression, and Dalton's Law to partial pressures of oxygen: seeing those connections turns formulas into clinical reasoning.

Dive tables are provided at the test, so the skill being tested is correct table use, not memorization of table cells. Practice looking up repetitive-dive scenarios until you can do so quickly and without losing your place.

Clinical Core: Indications, Toxicity, Complications and Safety

Therapeutic Mechanisms and Accepted Indications

The therapeutic mechanisms objective names six effects of oxygen at pressures above one atmosphere absolute: antimicrobial effects, vasoconstriction, hyperoxygenation, neovascularization, attenuation of reperfusion injury, and gas bubble reduction. You must also be able to classify each accepted indication by its proposed mechanism. That is a reasoning skill, not a list to memorize: ask which mechanism best explains why HBOT helps a given condition.

For indications, the objective requires listing all Currently Accepted Indications recognized by the Undersea and Hyperbaric Medical Society (UHMS) and knowing commonly used protocols (pressure, exposure time, and frequency) for each. One caution is important: the June 2024 manual contains legacy clinical narrative, including a reference to a 1992 indications report as the most recent. That is outdated. The public UHMS 15th-edition front matter is dated 2023 and lists later indications and updated references. Use the manual to define your preparation scope, but verify accepted indications, protocols and safety standards against current authoritative sources.

Sequencing Your Preparation by Domain

Because the official weighting is unpublished, schedule by dependency rather than guessing at percentages. Physics comes first because gas laws underlie barotrauma, toxicity, and decompression. Here is one sequence that builds each layer on the last. Adjust the pace to your own timeline, and see our CHRN study guide for a fuller approach.

For a compact last-pass review, our CHRN cheat sheet condenses the must-know facts. Once you have worked through the content, test yourself with realistic questions on the CHRN Exam Prep practice tests, and use the results to find which domains need another pass.

Keeping the Credential: Four-Year Renewal

Certification is not permanent. Renewal occurs every four years, and the currently linked August 2025 renewal form sets the requirements:

• An active RN license.
• Employer or medical-director confirmation of at least one year of hyperbaric experience, including 480 hours within the previous 12 months.
• 40 continuing education hours over the four years, including 20 Category A hours.

A lapse adds US$100 and removes member discounts. Note that the older manual's statement that ongoing hours need not be logged does not waive the newer form's employer-validated recent-practice requirement, so keep records from day one of your certification cycle.

Where the Credential Is Used

CHRNs work wherever hyperbaric oxygen therapy is delivered: hospital-based hyperbaric departments, wound care centers, and outpatient hyperbaric facilities that treat indications such as chronic wounds and other UHMS-accepted conditions. The certification is often valued by employers because the 480-hour experience requirement and preceptor validation show proven hands-on competence rather than coursework alone. If you are researching openings, see our CHRN jobs overview; for compensation and return on investment, our CHRN salary guide and analysis of whether the certification is worth it take a deeper look. No specific salary figures are asserted here because they vary by region, employer, and facility type.

Frequently Asked Questions