Mild HBOT vs medical HBOT.
1.3 ATA soft-shell vs 2.0 ATA hard-shell. The most-asked question about hyperbaric oxygen, answered honestly. Mechanism, evidence, who benefits from each, and where R1SE Kelham sits in the middle ground.
01 · The headline comparison
Side by side, in one table.
ATA = Atmospheres Absolute. Sea level is 1 ATA. 1.3 ATA is equivalent to descending 3m underwater; 2.0 ATA is 10m underwater.
02
What mild HBOT actually does (and what it doesn't)
1.3 ATA increases dissolved plasma oxygen meaningfully — just less than 2.0 ATA. The wellness benefit is real; the headline RCT evidence is not at this dose.
At 1.3 ATA breathing ambient enriched air (~30% O₂), plasma oxygen content increases roughly 50% above sea-level baseline. That's a meaningful step up — enough to drive some of the mechanisms behind HBOT's established benefits (improved cerebral perfusion, mild stem cell mobilisation, anti-inflammatory effects).
But it's also important to be honest: none of the headline RCTs (Hachmo telomeres, Hadanny cognition, Efrati post-concussion, Zilberman-Itskovich long-COVID) used 1.3 ATA. They all used 2.0 ATA on 100% oxygen. The cellular and clinical effects observed in those trials are dose-dependent — you cannot assume the same magnitude at half the pressure.
What the smaller mild-HBOT literature does support: better sleep quality, recovery support, reduced post-exercise inflammation, subjective energy and mood improvements, and a gentle on-ramp to chamber tolerance. These are real and reported consistently. They're just not the same magnitude as the medical-grade headlines.
03
What 2.0 ATA actually delivers
Every cited HBOT outcome study at the magnitudes you see quoted online used 2.0 ATA on 100% oxygen. That's the dose to think about when comparing to research claims.
At 2.0 ATA on 100% oxygen, plasma oxygen content rises roughly 10× sea-level baseline. Tissue oxygen pressure (the measure that actually drives the mechanism) rises 10–15×. This is the dose that delivers oxygen to tissues even when red blood cells can't reach them (the wound-healing story), drives 8× CD34+ stem cell mobilisation (Thom 2006), and produces the telomere and cognitive effects in the Tel Aviv trials.
Air breaks become important at this pressure. The Hadanny / Efrati session structure (typically 20 min on O₂, 5 min on air, repeated three to four times) is the active ingredient for the hyperoxic-hypoxic paradox — the mechanism many researchers now think drives the regenerative outcomes. Without the air breaks, you also accumulate oxygen toxicity risk on long sessions.
Hard-shell chambers (rigid, certified, capable of reaching 2.0+ ATA) are required for medical-grade protocols. Soft-shell envelopes physically cannot reach those pressures. This is the structural reason wellness providers who run soft-shell-only can't deliver the trial-grade dose.
04
The middle ground: 1.5–1.75 ATA
R1SE's hard-shell chamber lets us run at any pressure between 1.3 and 2.0 ATA. Most working protocols sit between 1.5 and 1.75 ATA — here's why.
1.5 ATA produces roughly 6–7× baseline plasma oxygen with a mask. That's most of the way to the 2.0 ATA dose, with shorter ear-pressure adjustment, lower oxygen-toxicity risk on long sessions, and more accessible recovery for first-time hard-shell users. It's the dose most members do most weeks.
1.75 ATA pushes closer to the trial-grade dose without committing to the full 2.0 ATA / 90-minute protocol. It's the sweet spot for cognitive performance, post-illness recovery, and athletic recovery sessions. Many members run a structured block at 1.75 ATA before committing to a longevity protocol at 2.0 ATA.
2.0 ATA is the dose for replicating the trial-grade evidence — the Hachmo telomere protocol, the Efrati post-concussion protocol, the long-COVID 40-session structure. This is where the cited RCT magnitudes live, and where the longevity-focused R1SE members invest.
05
Who benefits from which dose
There's no “best” pressure in the abstract — the question is what you're trying to achieve.
Choose 1.3 ATA (soft-shell) if: you're new to HBOT and want the gentlest possible introduction, you're recovering from a minor illness or training block, you're using HBOT as a relaxation / sleep-support tool, or you're combining HBOT with intense same-day training (lower interference with recovery signalling).
Choose 1.5–1.75 ATA (hard-shell) if: you want measurable recovery acceleration, you're running a structured 20–40 session protocol for cognitive performance, you're managing post-concussion or long-COVID symptoms (the lower-dose end of the Efrati protocols), or you're a competing athlete in a heavy training block.
Choose 2.0 ATA (hard-shell) if: you're committing to the Hachmo / Hadanny longevity protocol (60 sessions over 3 months), you're running an extended post-concussion or long-COVID programme under team supervision, or you have a specific evidence-driven goal that the trial-grade dose serves.
06
The honest position on wellness HBOT
R1SE's view: wellness HBOT is real, valuable, and worth doing — but it's not the same product as medical HBOT, and we don't pretend it is.
Most UK wellness HBOT providers run 1.3 ATA soft-shell chambers and market them with research that was conducted at 2.0 ATA. That's either a misunderstanding of dose-response or a deliberate elision. We don't do that — if we cite the Hachmo telomere finding, we tell you it's the 2.0 ATA dose and recommend the 2.0 ATA protocol if that's the outcome you want.
Conversely, we don't dismiss 1.3 ATA. The soft-shell has real value as a first-time entry, a recovery tool, a sleep-support intervention, and a regular maintenance dose. We just'd rather be honest about what each pressure does and let members choose with full information.
The structural advantage of R1SE Kelham is that we run both: soft-shell for entry, hard-shell up to 2.0 ATA for the trial-grade work. Most wellness providers force a binary choice. We don't.
Quick chooser
Pick a goal, get a starting pressure.
If your goal is
Wellness, sleep, entry
Start at
1.3 ATA
If your goal is
Recovery, performance
Start at
1.5–1.75 ATA
If your goal is
Longevity / post-concussion
Start at
2.0 ATA
A note on commitment: single sessions feel good at any pressure. The real effects compound across a 20–60 session block at the right dose. Match the protocol to the goal, not the marketing.
Common questions
Pressure matched to goal.
Our team will recommend the right pressure for what you're trying to achieve — not the marketing line.
Continue Reading
More from the R1SE HBOT Library
HBOT Knowledge Hub
Every hyperbaric oxygen page on the R1SE knowledge library.
ReadThe Science of HBOT
Telomere lengthening, cognitive enhancement, neuroplasticity — every claim cited.
ReadThe Benefits of HBOT
Cellular regeneration, recovery, anti-aging signals.
ReadConditions HBOT Treats
Post-concussion, long COVID, ulcers, stroke, fibromyalgia.
ReadHow to Use HBOT
Pressure, duration, frequency — from beginner to protocol-grade.
ReadTypes of Hyperbaric Chamber
Hard- vs soft-shell. 1.3 vs 2.0 ATA. Monoplace vs multiplace.
Read