Hyperbaric · 6 min read
Understanding ATA: What the Pressure Numbers Mean
ATA (atmospheres absolute) is a unit of total pressure measured relative to a vacuum, where everyday sea-level air pressure equals 1.0 ATA.
Quick answer
- 1.0 ATA is normal sea-level pressure; 1.3 ATA is about 30% higher, 1.5 ATA about 50% higher, and 2.0 ATA is double.
- Mild wellness use typically stays in the 1.3–1.5 ATA range.
- A chamber's maximum rated ATA helps you match it to your space and intended use.
When you compare hyperbaric chambers you'll see pressures listed in ATA. Here's a simple explanation of what those numbers describe.
ATA in plain terms
ATA stands for 'atmospheres absolute.' It measures total pressure relative to a vacuum. At sea level, the air around you is about 1.0 ATA.
A chamber rated at 1.3 ATA holds pressure roughly 30% above sea level; 1.5 ATA is about 50% above; 2.0 ATA is double sea-level pressure.
Why the range matters
Higher pressure means more oxygen dissolves into the body's fluids. Mild wellness use typically stays in the 1.3–1.5 ATA range, while higher pressures are associated with professional, clinical-grade equipment.
Knowing a chamber's maximum rated pressure helps you match it to your intended use and confirm it fits the space and operating routine you have in mind.
ATA, PSI, and other units you'll see on spec sheets
Manufacturers describe the same pressure in different units. 1.0 ATA equals roughly 14.7 PSI of absolute pressure — so a 1.3 ATA chamber adds about 4.4 PSI above ambient, and a 1.5 ATA chamber adds about 7.4 PSI. Some spec sheets list only the added (gauge) pressure, so check whether a number is absolute or above-ambient before comparing models.
You may also see kilopascals (kPa) on imported equipment: 1.0 ATA is about 101 kPa. A '30 kPa' soft-shell chamber and a '1.3 ATA' chamber are describing essentially the same operating point.
An everyday reference point
Pressure changes are easier to picture with familiar comparisons. Descending roughly 10 feet under water adds about 0.3 ATA — so a 1.3 ATA session is comparable in pressure terms to sitting about ten feet below the surface of a pool. In the other direction, a commercial airliner cabin is pressurized to about 0.75–0.8 ATA, noticeably below sea level.
That is also why your ears notice the transition: the same gentle 'ear pop' you feel on a plane's descent is what equalizing feels like as a chamber comes up to pressure.
How rated ATA relates to chamber construction
Soft-shell (fabric) chambers are typically rated in the 1.3–1.5 ATA range; that ceiling is a product of the zippered fabric construction. Hard-shell chambers use rigid vessels and can carry higher ratings, which is one reason they cost and weigh more.
A chamber's rated ATA is an operating specification of the equipment — like a tire's pressure rating — not a recommendation for how anyone should use it. If you're comparing models, our soft vs hard shell guide walks through how the rating interacts with size, portability, and budget.
Common questions
Is a higher ATA always better?
Not necessarily — 'better' depends on your goals, the equipment's design, and how it will be used. Mild wellness use commonly stays in the 1.3–1.5 ATA range.