Hyperbaric Chamber Risks: What You Need to Know

Hyperbaric Chamber Risks Are Real, and Mostly Manageable

Hyperbaric chamber risks include ear barotrauma, temporary visual changes, and oxygen toxicity. A proper pre-session assessment does most of the protective work. Understanding what can go wrong helps you make a clear-headed decision rather than one driven by either dismissal or unnecessary fear.

Why Pressure Is the Starting Point

Inside a hyperbaric chamber, your body breathes pure or near-pure oxygen at elevated pressure, which is how dissolved oxygen reaches tissues that normal blood flow cannot adequately supply.

That same pressure is also the source of most of the risks. Any air-filled space in the body, your ears, sinuses, and lungs, has to adjust as pressure changes. When that adjustment is smooth, there is no problem. When it is not, discomfort or injury can follow.

For a broader look at the therapy itself, see our guide on what a hyperbaric chamber is, including types, pressure levels and what the experience is actually like.

The Most Common Side Effects

The Undersea and Hyperbaric Medical Society (UHMS) documents the side effects most people encounter:

• Ear and sinus barotrauma: pressure discomfort or pain during pressurisation, similar to descending in a plane. Equalisation techniques, or slowing the compression rate, usually resolve it.
• Temporary myopia: some people notice their vision becomes slightly more short-sighted after a course of sessions. This reverses within weeks of finishing treatment.
• Fatigue or lightheadedness: mild tiredness after a session is common and generally resolves with rest.
• Confinement discomfort: feeling enclosed is not a medical risk, but it is worth discussing with the clinical team before your first session.

These effects are the reason pre-session screening exists. NHS England's clinical commissioning policy for hyperbaric oxygen therapy sets out the recognised risks alongside the clinical case for treatment.

The Rarer but More Serious Risks

Serious adverse events are uncommon in supervised outpatient settings, but they are not impossible.

Oxygen toxicity can affect the central nervous system or the lungs if a person is exposed to very high oxygen concentrations for too long. Symptoms of CNS oxygen toxicity include visual disturbances, tinnitus, nausea, and, in extreme cases, seizures. This risk is closely tied to pressure level and session duration. Staying within established protocols reduces it substantially.

Pulmonary barotrauma is a risk for anyone with air trapping in the lungs, for example from certain types of emphysema or an untreated pneumothorax. Expanding trapped air during decompression can cause serious lung injury. This is why untreated pneumothorax is an absolute contraindication to HBOT.

Fire risk is worth naming plainly. Pure oxygen environments are highly flammable. Reputable clinics prohibit all ignition sources, synthetic fabrics, and personal electronics inside the chamber. This is a facility safety issue, not a physiological one, and a well-run clinic will brief you on it before you enter.

The UHMS indications resource sets out the clinical framework that governs safe HBOT practice and the conditions for which it is indicated.

Risks at a glance

What to ask before your first session

1. What pressure do you run, and for how long? Oxygen toxicity risk is tied to both.
2. Who screens me, and for what? Untreated pneumothorax and some lung conditions rule people out entirely.
3. What happens if I cannot equalise my ears?
4. What are your chamber fire precautions? A well-run clinic briefs you before you enter.
5. What is the evidence for the specific reason I am coming? For wellness and recovery uses it is limited, and you should be told that plainly.

UK Standards

NHS England has published clinical commissioning policy covering specific HBOT indications and associated risk considerations. Choosing a clinic that operates within established clinical frameworks is a practical safety step.

Who Should Not Use a Hyperbaric Chamber

Absolute contraindication:

• Untreated pneumothorax

Relative contraindications (requiring careful assessment before proceeding):

• Chronic obstructive pulmonary disease with air trapping
• Uncontrolled seizure disorder
• Active upper respiratory infection or blocked sinuses
• Certain ear conditions or recent ear surgery
• Some cardiac conditions
• Confinement anxiety severe enough to prevent safe participation

This is not an exhaustive list. A clinical assessment before your first session is the only reliable way to identify whether any of these apply to you.

How Supervised Sessions Reduce Risk

HBOT is a medical intervention, not a wellness product that bypasses clinical judgement. The factors that keep risk low are straightforward:

1. A pre-treatment health screen to identify contraindications
2. Qualified clinical oversight during every session
3. Pressure and duration kept within established protocols
4. Clear patient briefing on equalisation techniques and what to report
5. Immediate access to support if a side effect occurs

For a fuller picture of what can go wrong and how often, our post on HBOT side effects and safety covers the evidence in more detail.

The Cardiff Context

If you are considering HBOT in Wales, the setting matters as much as the technology. IronOx Clinic in Cardiff operates with clinical oversight at every session. Before you use the chamber, the team reviews your health history to check for contraindications, explains the process, and stays present throughout. You can read more about HBOT at IronOx Clinic and what a session involves in practice.

If you are also exploring HBOT for a specific purpose, our post on what the evidence actually shows for HBOT benefits sets out where the research stands.

A Practical Summary

Hyperbaric chamber risks sit on a spectrum. Ear discomfort during pressurisation is common and manageable. Oxygen toxicity and pulmonary barotrauma are serious enough to take seriously, which is why supervised outpatient settings with qualified oversight matter. The single most effective risk-reduction step is a thorough clinical assessment before you start, carried out by someone who knows what to look for.

If you have questions about whether HBOT is appropriate for your situation, a no-obligation consultation is the right first step.

Automated clinical evidence review completed before publication.