1.3 ATA vs. 1.5 ATA vs. 2.0 ATA: What the Pressure Levels Actually Mean

Short answer: ATA (atmospheres absolute) measures total pressure, with 1.0 ATA equal to normal air pressure at sea level. Soft-shell chambers we carry are rated from 1.3 ATA (about 4.4 PSI above room pressure) up to about 1.5 ATA. Hard-shell chambers are rated up to 2.0 ATA and are generally used under supervision.

Last reviewed: September 2026. Educational only, not medical advice. See our disclaimer.

What ATA and PSI mean

ATA is a multiple of normal sea-level air pressure. PSI (pounds per square inch) is the unit most chamber gauges display, usually as the pressure above the room. Sea-level air pressure is about 14.7 PSI, so one atmosphere equals 14.7 PSI.

To convert: PSI above room = (ATA − 1) × 14.7. For 1.3 ATA, that is 0.3 × 14.7, or about 4.4 PSI.

The common levels

Where the chambers we carry fall

See each listing in Every Hyperbaric Chamber We Carry.

What “mild” means

“Mild hyperbaric” usually describes chambers that operate up to about 1.3 ATA, though some soft-shell chambers are rated higher. Summit to Sea holds its chambers at 4.4 PSI (1.3 ATA) using a double vent system and pressure release valves, with gauges that show the pressure inside. Mild does not mean the pressure is unimportant. A chamber is still a pressurized environment, and you should follow the manufacturer's manual.

Why higher is not automatically better

Higher pressures increase the risks of ear and lung injury and of oxygen toxicity, which is why hospital treatments use trained staff and monitoring. The FDA clears hyperbaric chambers for a specific list of medical conditions, and clearances are tied to how the equipment is used. Which pressure suits any person is a question for a physician.

A note on altitude

ATA is measured against sea-level pressure, but a chamber gauge shows pressure above the surrounding air. At altitude the air is thinner, so a chamber that adds 4.4 PSI reaches a lower total pressure than it would at sea level. If you live well above sea level, ask the manufacturer how the chamber is rated and what to expect.

What to check before you buy

• The working pressure in both ATA and PSI, and how the chamber limits it.
• Whether a prescription is required. Per the manufacturer, Summit to Sea chambers are Class II devices and require one.
• What oxygen supply you need. A 10 LPM at 20 PSI oxygen generator is required for Summit to Sea and is sold separately.

See the full range in our hyperbaric chamber collection or read the Hyperbaric Chamber Guide.