3A health · Technical reading guide · Updated 18 October 2026
Read the pressure reference before comparing chambers
A pressure specification needs both a unit and a reference. ATA indicates an absolute-pressure convention; kPa, MPa and bar need an additional absolute or gauge label. A bare number such as “0.03 MPa” is incomplete for comparing quotations.
This guide helps buyers read mild hyperbaric chamber specifications. The examples are arithmetic only and do not state the operating pressure of any 3A health model or prescribe equipment settings.
What do ATA, kPa, MPa and bar mean?
- ATA: atmospheres absolute. In this guide, 1 ATA means an absolute pressure of 1 standard atmosphere. Confirm that the supplier uses the same convention. DAN uses the abbreviation ATA for atmospheres absolute.
- kPa and MPa: kilopascals and megapascals. 1 MPa = 1,000 kPa.
- bar: 1 bar = 100 kPa. A standard atmosphere is 101.325 kPa, so bar and atm are not identical. NIST conversion factors.
Absolute pressure versus gauge pressure
Absolute pressure uses an ideal vacuum as its reference. Gauge pressure uses the surrounding atmospheric pressure. Their relationship is: absolute pressure = gauge pressure + ambient atmospheric pressure. WIKA explains the pressure references.
For quotation comparison, write the reference alongside the value, for example “30.40 kPa gauge” or “131.72 kPa absolute”. Do not infer the reference merely from the unit or the appearance of a pressure gauge.
Worked example: what is 1.3 ATA in kPa and MPa?
Using 1 standard atmosphere = 101.325 kPa:
- Absolute pressure: 1.3 × 101.325 = 131.7225 kPa = 0.1317225 MPa.
- Gauge pressure, only if ambient pressure is 101.325 kPa: 131.7225 − 101.325 = 30.3975 kPa = 0.0303975 MPa, approximately 0.304 bar.
Conversely, 0.03 MPa gauge is approximately 1.296 ATA under that same ambient assumption. It may be rounded to 1.3 ATA in an example, but the two values are not exactly equal. 1.3 ATA does not mean 0.3 MPa, and it does not mean 1.3 bar.
A small conversion table for reading specifications
| Example ATA | Absolute pressure / kPa | Gauge pressure / kPa | Gauge pressure / MPa |
|---|---|---|---|
| 1.2 | 121.59 | 20.27 | 0.02027 |
| 1.3 | 131.72 | 30.40 | 0.03040 |
| 1.5 | 151.99 | 50.66 | 0.05066 |
Values are rounded for display. The table assumes a standard ambient pressure of 101.325 kPa; it is not a list of available pressures, recommended settings or model capabilities.
Why the installation location matters
Ambient pressure varies with altitude and weather. The general conversion is gauge pressure in kPa = ATA × 101.325 − actual ambient pressure in kPa. Subtracting 101.325 kPa is valid only under the stated standard-ambient assumption. Reference: WIKA pressure types.
When reviewing a project at a different location, ask the supplier to confirm the model documentation, display reference and site assumptions. Do not use a conversion table to change operating limits or control settings.
What to request before comparing two quotations
- Exact model and version: match the cabin, external unit and supplied configuration.
- Complete pressure statement: number, unit, absolute or gauge reference, and any ambient assumptions.
- Purpose of the figure: identify whether it describes rated working pressure, design pressure or a test condition; request the corresponding document.
- Display information: ask what the controller and pressure gauge actually display.
- Project record: keep the agreed specification sheet with the layout, equipment list and quotation.
Common questions
Does ATA tell me the oxygen concentration?
No. A pressure figure is not an oxygen-concentration measurement. Request oxygen concentration, measurement location and supply method separately; a generator outlet value should not be presented as the chamber environment value.
Can the example table be applied to every 3A health chamber?
No. Check each model’s confirmed specification and supplied system. The worked examples do not establish the pressure range of the SA-MHC-MINI, SA-MHC4L or any other product.
Which information should I send for a model comparison?
Send the intended occupancy, installation city, room or access layout, preferred model and the pressure statement you need clarified. Ask 3A health to return a model-specific configuration and quotation.
Continue planning your chamber project
Compare chamber layout, specifications and cost · Check the installation site
Browse mild hyperbaric chamber models · Ask 3A health to clarify a specification
Sources and scope
NIST: conversion factors for atm and bar; WIKA: absolute and gauge pressure; DAN: ATA terminology. Sources checked 18 October 2026. The conversions above were calculated for this article.
This page explains units and procurement documents. It does not provide a clinical protocol, personal suitability assessment or instructions for operating or modifying a pressure system. Use the specific model’s documentation and qualified support for those decisions.
