A pressure chamber is a sealed enclosure designed to raise or lower air pressure around a person’s body, most commonly used in medicine to deliver high-pressure oxygen therapy. The medical version, called a hyperbaric chamber, typically operates between 2 and 3 atmospheres absolute (ATA), meaning the air pressure inside is two to three times what you experience at sea level. Pressure chambers also have important roles in aerospace training, deep-sea diving operations, and scientific research.
How Pressure Chambers Work
The physics behind a pressure chamber comes down to two principles about how gases behave. First, when you increase the pressure around a gas, the gas compresses into a smaller volume. Inside a hyperbaric chamber, this means any gas bubbles trapped in your blood or tissues physically shrink. Second, higher pressure forces more gas to dissolve into liquids. In your body, that liquid is blood plasma. When you breathe pure oxygen inside a pressurized chamber, your blood absorbs far more oxygen than it normally could, delivering it to tissues that may be starved or damaged.
These two effects work together. Shrinking unwanted gas bubbles provides immediate relief in conditions like decompression sickness, while the flood of dissolved oxygen supports healing in wounds, infections, and radiation injuries. The chamber itself simply creates the environment. The real therapeutic agent is the pressurized oxygen reaching your cells.
Types of Pressure Chambers
Monoplace Chambers
These are single-person units, usually made of clear acrylic so the patient can see out and staff can see in. They’re relatively compact, cost-efficient, and don’t require an attendant inside the chamber. The tradeoff is patient isolation. If you’re critically ill, medical staff can’t easily reach you or use standard monitoring equipment during treatment. Intravenous lines have to pass through the chamber wall to specially designed pumps outside, which can make precise medication delivery more difficult.
Multiplace Chambers
These are room-sized steel chambers that hold multiple patients and at least one medical attendant. Critically ill patients do better in multiplace chambers because staff can provide hands-on intensive care throughout the session, using standard hospital equipment inside the pressurized space. The downside is scale: they require significantly more space, staffing, and upfront investment.
Portable Soft-Shell Chambers
Inflatable, zippered chambers marketed for home use reach only about 1.5 to 1.7 ATA. That falls well short of the 2 ATA minimum required for approved medical indications. Hard-shell clinical chambers reach 2 to 3 ATA, which is where genuine therapeutic effects begin. Soft-shell chambers are approved only for acute mountain sickness, and the limited pressure they generate makes them unsuitable for treating wounds, infections, or diving injuries.
Hypobaric (Low-Pressure) Chambers
Not all pressure chambers increase pressure. Hypobaric chambers do the opposite, reducing air pressure to simulate high altitude. Military and commercial aviation programs use them to train pilots and aircrew to recognize the symptoms of oxygen deprivation before it becomes dangerous. In a typical session, the chamber simulates an altitude of around 25,000 feet. After breathing pure oxygen for a period to clear nitrogen from the body, participants remove their masks and breathe the thin ambient air while performing tasks. The goal is to experience firsthand how quickly thinking and coordination deteriorate at altitude, so they can recognize the warning signs in a real emergency and get back on supplemental oxygen before losing the ability to act.
Medical Uses
Hyperbaric oxygen therapy has 14 approved indications covering a range of emergencies and chronic conditions. Some of the most common include:
- Decompression sickness: The classic “bends” from scuba diving, where nitrogen bubbles form in blood and tissues during a too-rapid ascent. The chamber shrinks those bubbles while flooding the body with oxygen, reducing swelling and restoring blood flow to damaged areas.
- Carbon monoxide poisoning: Carbon monoxide binds to red blood cells roughly 200 times more tightly than oxygen does. High-pressure oxygen displaces it far more effectively than breathing normal air.
- Gas gangrene and necrotizing soft tissue infections: These life-threatening infections involve bacteria that thrive in low-oxygen environments. Saturating tissues with oxygen helps fight the infection directly.
- Problem wounds: Diabetic foot ulcers, radiation injuries to soft tissue and bone, and compromised skin grafts or flaps can all benefit when standard treatment stalls.
- Air or gas embolism: When a gas bubble enters the bloodstream (during surgery or from a lung injury), increased pressure reduces the bubble’s size and helps the body reabsorb it.
- Severe anemia: When blood transfusion isn’t possible, pressurized oxygen dissolved directly in plasma can bridge the gap.
- Sudden hearing loss: Idiopathic sudden sensorineural hearing loss, where hearing drops without a clear cause, is one of the newer approved indications.
Other approved conditions include crush injuries, compartment syndrome, acute burns, central retinal artery occlusion (a type of eye stroke), intracranial abscess, and refractory bone infections that haven’t responded to conventional treatment.
What a Treatment Session Feels Like
A typical session lasts 60 to 90 minutes at pressure, though some protocols for decompression sickness or gas embolism run longer. As the chamber pressurizes, you’ll feel fullness in your ears, similar to descending in an airplane. Swallowing, yawning, or gently blowing against pinched nostrils helps equalize the pressure. In a monoplace chamber, you lie inside a transparent tube and breathe the oxygen that fills the space. In a multiplace chamber, you sit or recline and wear a hood or mask that delivers pure oxygen while the room itself is pressurized with regular air.
Most people describe the experience as uneventful. You can watch TV, listen to music, or simply rest. The pressurization and depressurization phases at the beginning and end of each session are when most discomfort occurs, and staff control the rate to keep it tolerable.
Side Effects and Risks
The most common side effect is ear discomfort or middle ear barotrauma. A systematic review found that people receiving hyperbaric oxygen therapy were about 3.4 times more likely to experience ear discomfort than those receiving a placebo treatment. This ranges from mild pressure and pain to, in rare cases, a ruptured eardrum. Any air-filled space in the body, including the sinuses, teeth, and lungs, can be affected by pressure changes, though ear problems are by far the most frequent.
Vision changes are the second most common issue, with a roughly 2.4-fold increased risk compared to controls. Many patients develop temporary nearsightedness after a series of treatments. This typically reverses within weeks to months after therapy ends.
Oxygen toxicity is rarer but more serious. At high pressures, concentrated oxygen can irritate the lungs or, in uncommon cases, trigger seizures. The risk of seizures was slightly higher in hyperbaric groups in clinical studies, though the difference was not statistically significant. Claustrophobia can also be an issue, particularly in monoplace chambers.
Fire Safety Inside the Chamber
The combination of elevated pressure and near-pure oxygen creates a significant fire hazard. Materials that would never ignite under normal conditions, including silicone rubber, certain lubricants, and flame-resistant fabrics, can catch fire inside a pressurized, oxygen-rich chamber. For this reason, facilities enforce strict rules about what enters the chamber. Patients typically change into approved cotton garments, and electronics, lighters, petroleum-based products, and synthetic fabrics are prohibited. Staff follow detailed fire prevention protocols covering everything from grounding requirements to the specific materials used in bedding and equipment.