How to Convert Oxygen Percentages to Pressure

Knowing the percentage of oxygen in an enriched air nitrox mix can avoid potential life-threatening situations when underwater. Oxygen becomes toxic when breathed at depths of more than 6 m. The pressure of oxygen in a tank can be worked out by knowing the percentage of the oxygen in the mix, and then converting this number to a partial pressure (the pressure of the oxygen in the tank). You can make the conversion using only one sum.

Things You'll Need

  • Oxygen analyzer
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Instructions

    • 1

      Place an oxygen analyzer in front of the tank valve of an enriched air mix. Slowly turn the valve on. Let the air run through the analyzer until the number displayed is constant. Write down the percentage of oxygen on the tank.

    • 2

      Convert the percentage to a partial pressure. If a tank holding the mix is 100 percent, then the oxygen in the mix makes up a portion of that. For example, 24 percent oxygen exerts a partial pressure of 0.24.

    • 3

      Work out the pressure of the oxygen in the tank using the partial pressure. For example, if a tank has 200 bar in it, and the percentage of oxygen is 25 percent, then you need to multiply the tank pressure by 0.25 to know how much of the pressure is oxygen. In this case the oxygen has a pressure of 50 bar.