A prerequisite for this course is to complete your Nitrox certification first. Terms like Partial Pressure, Maximum operating depth and equivalent air depth should be familiar.
Mixing your own Nitrox
If you want to mix your own Nitrox, then one of the ways to do so is by putting some oxygen in an empty tank before connecting it to the compressor and filling it up.
You could rent a standard 50-liter oxygen tank and fit a canting hose to pass oxygen.
There is enough information on the web on how to do this in a safe and exact way.
Example: You want to make 200 bar of EAN40, that is 40% 02 and 60% N2, how to do that?
Air already has 21% so you want to add 19% to make it 40%
19 % of 200 bar is 38bar : First put 38bar of oxygen in an empty tank and then pump air on top of it till 200 bar.
HeliAirHeliAir, sometimes referred to as “poor man’s Trimix”, is a breathing gas mixture consisting of helium and air, the latter actually being made up of only oxygen and nitrogen. While the same three gases are also found in Trimix, Heliair is different because it is mixed differently. Trimix is blended by decanting helium and oxygen and nitrogen into the scuba tank and then topped off with air. HeliAir, on the other hand, is blended more easily by filling the scuba tank with the desired amount of helium and then adding air. Consequently, air has a fixed 21:79 ratio of oxygen to nitrogen before being added to the tank.
Example: You want to make 200 bar of trimix for a dive to 90 meter (10bar), you don't want the PP02 to go above 1.4 bar
1.4 / 10 bar = 0.14 bar the oxygen percentage in the tank should not be more then 14% Normally air has 21% Oxygen so 7% will have to be Helium 7% of 200 bar is 14 bar. You need to flow 14 bar of helium in the tank before pumping air on top of it.
Accounting for temperature change:
When you fill a scuba tank it heats up, after it cools down the pressure will reduce. To calculate how much it will reduce us the universal gas law Pressure / Temperature = Constant (For temperature convert to Kelvin (+273 degrees)
Example: After filling a tank to 200 bar its temperature is 47 degrees Celsius (+ 273 that's 320K) after cool down the temperature is 27 degrees Celsius (+ 273 that's 300K)
200 / 320 = 0.625 0.625 x 300 = 187.5 bar
Extra Info
Oxygen Clean Equipment: This equipment has been cleaned from flammable greases and oils.
Avoid pure oxygen entering a compressor: When pumping air with a compressor into a tank that already has pure oxygen inside, wait for the compressor to build up enough pressure before opening the valves, in that way the oxygen won't flow in to the compressor. The compressor is not oxygen clean and should not get exposed to pure oxygen.
Oxygen Analyzers: Oxygen analyzers have a sensor that expires after a certain amount of contact with oxygen. By storing the oxygen analyzer in an airtight box, it will last longer.
