CHRN Study Guide 2026: How to Pass on Your First Attempt

What You Are Actually Studying For

The Certified Hyperbaric Registered Nurse credential is the basic nursing certification in hyperbaric medicine. The Baromedical Nurses Association Certification Board (BNACB) oversees nursing eligibility and certification, while the National Board of Diving and Hyperbaric Medical Technology (NBDHMT) administers and grades the examination. If you want the big-picture definition first, our overview What Is CHRN Certification? covers it, and What Does CHRN Stand For? clears up the acronym, which several unrelated credentials share. Everything here concerns the hyperbaric nursing credential only.

The most important thing to understand about preparing is that this exam tests a blend of nursing judgment and technical, physical and operational knowledge. A candidate who only knows wound care and patient assessment will be exposed on gas laws, decompression tables and chamber fire safety. A candidate who is a strong diver or technologist but weak on nursing process and pharmacology will be exposed on the other end. The study guide below is built to close both gaps.

Exam Format, Registration and Fees

What the test looks like

The exam consists of 120 items in multiple-choice and true/false format, with a two-hour time limit and a 70% passing threshold. The manual explicitly excludes essay and short-answer questions. That means you are never asked to write out a protocol from memory; you must recognize the correct answer among options, which rewards precise discrimination between similar-sounding concepts (for example, Paul Bert effect versus Lorrain Smith effect). For a deeper look at the scoring line, see CHRN Passing Score 2026.

Several details are not publicly established, and you should not plan around guesses. The split between scored and unscored items is unknown, whether the test adapts to your answers is unverified, and the credential-specific pass rate is not publicly disclosed. A historical combined-program figure exists but is not CHRN-specific, so ignore anyone quoting it as your odds. Our write-up CHRN Pass Rate 2026: What the Data Shows explains what can and cannot be said.

Testing conditions

Testing takes place at a designated testing site; any in-house proctorship requires NBDHMT approval. This is not default unproctored home testing, so plan travel and scheduling accordingly. Supplemental dive tables are provided and a pocket calculator is allowed. Unrestricted open-book testing is not established, so do not assume you can bring your own reference material. Timing and windows are covered in CHRN Exam Dates 2026.

The June 2026 initial application confirms the three fee tiers and requires membership evidence for the discounted rates. Because the repeat-exam fee comes from the older manual and no newer figure was found, confirm it with NBDHMT before you budget for a retake. A fuller cost picture, including renewal, is in CHRN Certification Cost 2026.

The Eligibility Gate Comes Before Studying

Many nurses begin studying before confirming they qualify to sit. Do the reverse. The prerequisites are substantial, and the 40-hour course and 480 experience hours are eligibility requirements, not part of the two-hour exam. The requirements as retrieved:

• An unrestricted RN license.
• Two years of hospital or clinic experience, or one year of critical care.
• A recent active hyperbaric year.
• An approved 40-hour introductory course, or applicable 40 Category A replacement credits.
• 480 post-course direct patient-care hours, with qualified preceptor approval.
• An employer recommendation.

The full walkthrough is in CHRN Requirements 2026: Eligibility, Prerequisites & How to Qualify. The practical implication for study planning is that your 480 hours and your preparation period overlap. Use your clinical hours as active study: when you perform a pre-treatment checklist at the chamber, mentally map it to the patient-protection objectives in the manual. If you are still choosing a course, see CHRN Training.

Build Your Study Plan Around the Resource Manual

The single most useful document is the NBDHMT CHRN Resource Manual. The currently linked version is dated June 2024. It reproduces terminal objectives for each topic, and those objectives are the closest thing to a syllabus you will find. Read them as verbs: "differentiate," "convert," "utilize," "list," "recognize." Each verb tells you the level at which a question can be asked.

Two cautions apply. First, the manual contains legacy clinical narrative, including a reference to a 1992 indications report as the most recent. That statement is outdated, since the UHMS 15th-edition Indications front matter is dated 2023 and lists later indications and updated references. Use the manual to establish scope, then verify accepted indications, dosing, and nursing and safety standards against current authoritative sources. Second, do not treat the manual's sample questions as live examination content or memorize them as if they were.

The sixteen topics, in order, are: history; physical aspects; physiological aspects; decompression theory; therapeutic mechanisms; accepted indications; oxygen toxicity; other complications; the hyperbaric facility; safety for the environment; safety for the patient; NFPA guidance; transcutaneous oxygen monitoring; nursing management; BNA standards of practice; and operation of monoplace and multiplace chambers. For a domain-by-domain breakdown, see CHRN Exam Domains 2026: Complete Guide to All 16 Content Areas. The manual gives full chapter bodies for most of these but not separate bodies for the NFPA, BNA standards and chamber-operation entries, so you must source those from the external standards themselves.

Physics, Physiology and the Math You Must Do by Hand

Because a pocket calculator is allowed, you will not be doing long arithmetic in your head, but you must know which formula applies and which temperature scale a gas-law problem requires (absolute scales, in practice). Practice by writing out each law's relationship in words first, then setting up the problem. Most errors come from using gauge pressure where absolute pressure is needed, so make "gauge versus absolute" a reflex check at the start of every problem. Our CHRN Cheat Sheet condenses the conversion relationships onto one page for repeated review.

The history topic is small in scope but easy to overlook. The manual asks you to identify contributions associated with Behnke, Bert, Boerma, Bond, Boyle, Brummelkamp, Fontaine, Haldane, Henshaw and Yarborough. Build a simple name-to-contribution list and review it a few minutes at a time. It is cheap to learn and a reliable source of straightforward points.

Decompression Tables and Therapeutic Mechanisms

Practice walking through repetitive-dive scenarios: find the repetitive group, apply the surface interval, read the residual nitrogen time, then determine the resulting limit. Do this on paper with the tables open, repeatedly, until the lookup sequence is fluent. Equally important is the conceptual point that the tables reduce but do not eliminate decompression sickness risk, which is a classic true/false target.

The manual also expects you to classify each accepted indication by its proposed therapeutic mechanism. That is a high-value study exercise: build a two-column chart matching each indication to the mechanism most associated with its benefit, so that a scenario question about, say, a crush injury or a gas bubble disease immediately points you toward the right mechanism.

Indications, Oxygen Toxicity and Barotrauma

Accepted indications

You must be able to list the indications the Undersea and Hyperbaric Medical Society currently considers appropriate for referral, and to know commonly used treatment protocols in terms of absolute pressure, exposure time and frequency. Because the manual's own narrative is dated, anchor this list to the current UHMS Indications publication rather than the older manual text. Study each indication as a small card: the condition, the mechanism, and the typical pressure, duration and treatment-frequency pattern.

Oxygen toxicity

The distinction between central nervous system toxicity (the Paul Bert effect) and pulmonary toxicity (the Lorrain Smith effect) is a perennial exam theme. Know how each presents clinically, the methods used to extend patient tolerance to hyperbaric exposure, and the prevention and management principles for both. Be especially clear on premonitory signs of CNS toxicity, since recognizing them before a seizure is both a patient-safety priority and a likely question topic.

Other potential complications

This topic centers on gas-filled spaces. You should be able to recognize every anatomic and equipment gas-filled space or potential space before compression, minimize barotrauma through patient education and appropriate venting of equipment, and recognize potential airway compromise, particularly during decompression, along with the immediate management that reduces pulmonary barotrauma risk. Also understand how CNS oxygen toxicity and reactive airway disease complicate decompression.

Chamber Safety, Facility Knowledge and NFPA

Fire prevention in an oxygen-enriched environment is among the most consequential content in the exam. Link it directly to the NFPA hyperbaric chamber guidance named in the manual's contents. Because the manual does not provide a separate detailed body for NFPA, obtain the current guidance itself and confirm you can explain, in plain language, why materials, static and ancillary electronics matter. Likewise, operation of monoplace and multiplace chambers is a listed topic without its own chapter body, so lean on your facility's operating procedures and your course materials.

Nursing Management, TcPO2 and BNA Standards

The BNA Hyperbaric Nursing Standards of Practice, available on the BNA website, are a listed topic without a separate chapter body in the manual. Read them directly and tie each standard to something you do on shift: assessment, documentation, patient education, safety. If you are weighing the credential against career goals, CHRN Jobs and Is the CHRN Certification Worth It? are useful companions, and CHRN Salary Guide 2026 covers earnings context.

A Domain-Sequenced Study Schedule

Rather than a generic schedule, sequence the work by dependency: physics supports physiology, physiology supports decompression and toxicity, and all of it supports the safety and nursing topics. The plan below is editorial, not an official weighting, and you should compress or stretch it to fit your test date.

When you are ready for timed practice, the CHRN practice test site lets you rehearse the two-hour pace and see which topics need another pass. Treat each missed question as a pointer back to a specific manual objective rather than as an isolated fact to memorize. Because the questions are multiple-choice and true/false, practice eliminating distractors: on a calculation item, check units first; on a safety item, ask which option best protects the patient or the environment.

To calibrate expectations about workload, How Hard Is the CHRN Exam? discusses what makes the test demanding, and the CHRN Study Guide hub collects related preparation resources.

After You Pass: Renewal and Career Context

Certification is not permanent. Renewal occurs every four years and requires an active RN license, 40 continuing education hours including 20 Category A hours, and recent-practice validation including 480 hours in the previous 12 months, confirmed by employer or medical director. Per the August 2025 renewal form, fees are $150 for BNA members, $200 for UHMS or ACHM members and $250 for nonmembers; a lapse adds $100 and removes member discounts. Note that the older manual's statement that ongoing hours need not be logged does not override the newer form's employer-validated recent-practice requirement.

If you are new to the field and want the fundamentals of the credential itself, What Is CHRN? and CHRN Certification provide the background. Check the main practice site for ongoing question practice as you move toward your test date.

Frequently Asked Questions