While diving, oxygen is both essential and tightly controlled. The deeper you go, the more sensitive your body becomes to changes in oxygen levels, and even small deviations can shift a dive from safe to unsafe. The problem is that you cannot see or feel these changes on your own.
The solution for this is to have a proper oxygen analysis before diving. A reliable O₂ analyzer verifies what you are about to breathe and confirms that your mix is appropriate for your planned depth.
Most importantly, it helps you avoid the two main oxygen-related risks that divers must manage on every dive.
The Two Oxygen Risks Every Diver Must Manage
Every diver moves between two oxygen limits that cannot be seen or felt. These limits decide whether a dive stays within a safe range or crosses into danger. Those are:
1. Too Little Oxygen (Hypoxia)
To begin with, your brain needs a minimum oxygen partial pressure (Pₒ₂) of about 0.16 bar to stay conscious. When the oxygen content in your mix falls below this level, you may experience disorientation or a sudden loss of consciousness without any clear early warning.
This is especially important when working with Trimix or other hypoxic blends that contain less than 21 percent oxygen. Since these gases are designed for deeper dives, they become unsafe to breathe near the surface unless they are properly analyzed and planned.
2. Too Much Oxygen (Hyperoxia)
On the other hand, oxygen levels that are too high create the risk of hyperoxia. The safe upper limit for oxygen partial pressure depends on exposure time, workload, and equipment, but for most dives, typically under 3 hours, it is commonly set at around 1.4 bar. With up to 1.6 bar allowed for technical diving decompression stops.
When PO₂ rises beyond safe limits, oxygen becomes increasingly reactive and can lead to oxygen toxicity. Acute toxicity comes from short-term exposure to very high PO₂ and mainly affects the central nervous system (CNS), with early signs such as perioral twitching and spasms of small muscles in the hand. Chronic toxicity develops from longer exposure to moderately elevated PO₂ and affects the lungs.
Because every breathing gas has a Maximum Operating Depth (MOD) determined by its oxygen content, accurate oxygen analysis is essential for planning a dive that stays within these safe limits.
How to Analyze Oxygen?
Since managing oxygen limits depends on knowing exactly what is in your cylinder, the next step is understanding how oxygen analysis is performed.
Modern devices, such as the NRC PIC O₂ Analyzer, use an electrochemical sensor and a microcontroller to measure gas concentration.
Here is how the process works:
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Calibrate the Analyzer: Hold the CAL button for a few seconds until “CA” appears, then wait for the display to stabilize at 21 percent.
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Create a Gentle Gas Flow: Open the cylinder valve very slowly until you hear a light, steady flow of gas. A strong jet of gas is unnecessary and can affect the reading.
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Position the Analyzer: Place the T-piece or extraction set in front of the valve opening, ensuring gas can escape freely through the other side of the adapter.
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Wait for a Stable Reading: Hold the analyzer in the gas stream for a few seconds. When the number stops changing, the displayed value is the verified oxygen percentage in the cylinder.
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Care for the Device: If the valve threads are wet, dry them before use. Store the analyzer in a dry place.
For a clearer walk-through, you can also watch Stefan from NRC International demonstrate the full procedure down below!
Safe Diving Begins With Accurate Oxygen
Every safe dive starts with knowing the exact oxygen content in your cylinder. When you verify your mix, you set the foundation for a controlled dive profile and a safe operating depth.
Accurate readings only come from tools that deliver consistent, dependable performance. That is why so many divers rely on NRC analyzers. With stable measurements, fast response, and sensors engineered for real-world use, the NRC PIC O₂ Analyzer gives you the clear, trustworthy data you need before every dive.
Get your NRC PIC O₂ Analyzer and breathe with confidence from the first check!
