Understanding Your HBOT Pressure Gauge

Your chamber’s pressure gauge shows how much the pressure inside the chamber increases compared to the air around you.
This means the gauge shows relative pressure — the difference between inside and outside air — not the total pressure in absolute terms.

Relative vs. Absolute Pressure

At sea level, the normal air pressure is called 1.0 ATA.
When you go into the chamber and add pressure, you go above that level:

• 1.3 ATA means 30 % more pressure than normal air
• 1.5 ATA means 50 % more pressure than normal air

Your gauge starts from zero because it measures how much extra pressure is added on top of your local air pressure.

If you live or use the chamber in the mountains, the outside air pressure is naturally a bit lower (for example, around 0.9 ATA).
Your gauge still works correctly, because it measures the increase above your local pressure.
So even if your starting point is lower, when the gauge shows the same psi as at sea level, your body still experiences the same HBOT effect — the same percentage increase in oxygen pressure.

Gauge Units

Your gauge shows two scales:

• psi – pounds per square inch (outer scale)
• kPa – kilopascals (inner scale)

They both show the same thing in different units:

• 1 ATA ≈ 101 kPa
• 1 ATA = 14.7 psi

They’re just two different measurement systems — like Celsius and Fahrenheit.
The important thing is how these numbers relate to the ATA values you usually hear — for example, 4.4 psi (or about 30 kPa) on the gauge equals 1.3 ATA, which is a common mild HBOT pressure.

Gauge Reading to ATA Conversion

Gauge Colors and What They Mean

Your gauge has colored zones to help you see the pressure level at a glance:

• Green zone – 1.0 - 1.3 ATA
• Yellow zone – 1.3 - 1.5 ATA
• Red zone – Exceeds 1.5 ATA

Helpful Tips

• Always pressurize and depressurize slowly for comfort.
• After depressurizing only open the zippers when the needle is on zero

Alternative method: using the Barometer Plus app

You can use the Barometer Plus app to measure the exact pressure inside your chamber with your phone.
It’s a simple and accurate way to see the real atmospheric and chamber pressure in ATA (or ATM) units.

How It Works

Most newer smartphones have a built-in barometric pressure sensor, which the app uses to display real-time pressure readings. This allows you to check how your chamber’s gauge compares to the actual local air pressure.

Usually have barometer sensors:

• Samsung: Galaxy S-series, Note-series, Fold/Flip-series, many Galaxy A-series (e.g., A52, A72, A73)
• Apple: All iPhone 6 and newer
• Google: Pixel phones (all models)
• Huawei: P-series and Mate-series
• Xiaomi: Mi 10, Mi 11, Mi 12, Mi 13, some Redmi Note models
• OnePlus: 6 and newer
• Sony: Xperia flagship models
• Oppo / Vivo: Some Pro or flagship models

Steps:

1. Download the Barometer Plus app from Google Play or the App Store.
2. Open the app and go to Settings → Units, then select ATM (atmospheres).
   • ATM and ATA are practically the same unit for your purposes — both describe total air pressure.
3. Note the reading before your session (this is your local air pressure).
4. Observe the reading when the chamber is pressurized. The difference shows how much the pressure increased.

Important to Know

• Your chamber’s pressure gauge measures relative pressure — how much pressure was added on top of the surrounding air.
• The app shows absolute pressure, which includes the air around you + added chamber pressure.
• If you live at higher altitude (where air pressure is naturally lower than 1.0 ATA), your final number on the app will also be slightly below the nominal 1.3 or 1.5 ATA, even if your gauge shows normal values.
  • Example: if your local pressure is 0.95 ATA, and your chamber adds 0.3 ATA, the total will be about 1.25 ATA.
• Relief valves also have a normal variation of about ±0.02 ATA, so small differences are expected.

Summary

Using the Barometer Plus app helps you:

See the real-time pressure in ATA for peace of mindrelief valves is also lower than 1,3 ATA. Also the relief valves have +/- 0,02 ATA range of preciseness.

Confirm your chamber’s pressure accuracy

Understand local air pressure differences (especially at altitude)