Karlīs Rebreather Page

Gas Logistic for Oxygen-, Nitrox-, Trimix- & Heliox-Diving


Diving Nitroxetc. means filling the Bottles with a Gas different than Air.

This Website can not serve you with information about regulations for all four corners of the earth , so it only speaks about technical aspects.
I strictly recommend to qualify as gas-blender before blending gases.

Do not take Oxygen too easy, think about the Oxygen-Accidents on Apollo-1, Apollo-13 and the Oxygen-Generator Accident on the Space Station MIR.

 Take care that tanks only get filled with gases they are rated, cleaned and labelled for.

For most Divers getting a fill with Nitrox or any other gas is just walking into the diveshop and ordering the fill they want. But it is always good to understand how something works.


Nitrox Fills


Oxygen Fills


Trimix Fills


Heliox Fills

Heliox-Rebreather Diving is no expensive black magic, it is not much more expensive than running your CCR as Nitrox-Rebreather. Even in Germany you can afford to dive Heliox if you ride a CCR, a fill of a 50 liter 200 bar storage tank with Heliox16 costs about 200Euro here and should last for more than 20 dives.
Diving with Heliox is not a black magic at all, it's a responsible way to handle the problems gas-density and nitrogen-narcosis, but you need to know how to handle Helium Decompression-Tables and be wise enough not to reach out for HPNS.


Argon Fills


Filling small Bottles

The smaller the volume of your mix, the harder it is to perform a proper ratio. A solution for that problem with the small rebreather bottles is to create your mix in a set of doubles and decant into the smaller flasks.


Van der Waals-Gas Equation

a description for the behaviour of real Gases in the 10-6 bar to 103 bar Range. In the most cases it has a good performance (as long as the Isotherms are above the critical temperatures in the pV- Diagram; which is normally fulfilled for Helium, Nitrogen and Oxygen at diving applications, not for CO2, most of it is liquid at the pressure in a CO2-cartridge).

p:= Pressure, n:= Number of Mol's (a mol expanded gas means 22.4liter at 1bar), V:= Volume, a:= Van der Waals-Coeffizient for attraction-effects, b:= Van der Waals-Coeffizient for repulsion effects (~volume of the atoms/molecules of the gas), R:= Gas-constant = 8.314 J K-1 mol-1, T:= Temperatur [Kelvin]

For Gasmixes, that can be looked upon as a homogenous Gas (same Aggregate state, only Van der Waals-interrelations), the Van der Waals-Coeffizients can be estimated like this:

with xj, xi:= Molar-fraction of gas i and j, aij=(ai aj)1/2 and bij=(bi bj)1/2


a [dm6 bar mol-2]

b [10-2 dm3 mol-1]

Mass [Gramm/22.4bar*l]

O2   = Oxygen




N2   = Nitrogen




He   = Helium




Ar   = Argon




CO2= Carbon-Dioxide





Gas Analysis

has to be done (at minimum) twice when diving with mixed gases: 1) as part of the filling process, 2) prior to diving.
The predive analysis should be done by the diver, using instruments that are independent from those used during the filling.
When you are sure about the rest, a measurement of the oxygen-percentage is all what is needed, if you also want to check the Helium, a relative cheep solution is to measure the sonic speed. At 1bar the speed of sound is 326m/sec in Oxygen, 349m/sec in Nitrogen and 1309m/sec in Helium.
Being sure about the rest is the other important thing. You surely do not want to get a chronically oil-poisoning, a carbon-monoxide poisoning, water or oil in your tanks, so always check that you get your fills at a responsible and competent Filling station.




http://Rebreather.de/rebreather/gas_logistic.htm © Karl Kramer, 9.10.1998