Pressure, explained.

The unit

ATA means atmospheres absolute. At sea level you are at 1 ATA — roughly 1.013 bar, or 14.7 psi. A chamber at 1.5 ATA holds one and a half times that; at 2 ATA, twice. Because the scale is absolute rather than a gauge reading, 2 ATA is one additional atmosphere of applied pressure, not two.

The rough physical equivalent is depth in seawater: 1.5 ATA is about five metres down, 2 ATA about ten.

Why the number varies between chambers

Soft-sided, inflatable chambers are limited by their construction and generally stop between 1.3 and 1.5 ATA. Rigid chambers — steel or acrylic, built as certified pressure vessels — are designed for 2 ATA and beyond. That is a difference of engineering, of certification, and of price, and it is the first fork in any buying decision.

Pressure is not the whole session

Two chambers at the same pressure can give completely different sessions. What else changes it: how the oxygen is delivered and at what concentration, how long the session runs, how fast the chamber pressurises and depressurises, cabin temperature and humidity, and whether anything else is happening inside — light, magnetic fields, movement.

That last point is the whole argument for the Lifetech line, which puts five further modalities inside the pressurised shell rather than treating pressure as the entire proposition.

See the five-therapy chamber

Where the regulatory line sits

In the European Union, the pressure vessel itself falls under the Pressure Equipment Directive 2014/68/EU. Once a chamber is placed on the market for a medical purpose it is additionally a medical device under Regulation (EU) 2017/745, and higher pressures are generally handled on that route. In practice this is why the same chamber can be offered with a non-medical specification and a medical one, and why the certification status of your exact configuration is a question to settle in writing before ordering, not after.

What the research actually measured

If you read a study, read its protocol. Pressure, session length, number of sessions and oxygen fraction are all part of the result, and findings at one protocol say nothing about another. The frequently cited 2020 Tel Aviv University trial in Aging, for example, ran sixty daily sessions at 2 ATA with intermittent 100% oxygen — a specific and demanding protocol, not a description of hyperbaric therapy in general.

Nothing on this site is medical advice, and no equipment we advise on is presented as treating, curing or preventing any condition. Talk to a qualified physician about whether and how hyperbaric oxygen is appropriate for you.