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Potentially life saving Gas Blending formula

Let's face it, Gas Blending theory is boring and course providers offer a lot of word salad because they usually don't understand the mathematics or physics themselves.


If you are mixing Enriched Air (Nitrox), you don't need to pour back through the nonsense books. There are two options;


  1. Download Gary Kesslers free calculator, but this requires a computer with Excel. Do you want to stop diving if the computer goes down?

  2. Learn this formula;


Worked example;

I have an empty cylinder. I want to do an EANx36 dive (i.e. HMAS Brisbane). My cylinder is 232 bar, but no dive shop goes past 230, let's be honest, 220 bar.


This is my result;


A conservative blender (like me) would probably round this down to 41 (or even 40) bar. But this shows that I need 41.997 bar of Oxygen to achieve an EANx36.


Practice this with a calculator (unless you have a scientific one, you may have to do it one line at a time) in conjunction with EANx calculator software until you get the hang of it.


The one thing I hated getting taught to gas blend was "Bro, just put in 32 bar of O2, then fill the tank, that will give you EANx32". You don't know what your customer is going to do with Nitrox, they may be going right to the MOD of the gas, be precise.


No matter how you calculate it, always use an Oxygen Meter as well to confirm the final concentration.


Any questions? Dive@NorthernRiversDiving.com.au

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