Gases and mixes

The Gases page is where you declare the mixes you carry: air, nitrox, trimix, decompression gases, bailout gases and, in rebreather mode, the diluents.

Gas management page with the list of mixes

List of mixes

Mixes are sorted by decreasing oxygen content. Each one shows:

  • a switch to enable or disable it (only enabled gases are offered in the segments);
  • the name of the gas;
  • the composition: percentage of O2, of helium (He) and of nitrogen (N2, worked out automatically);
  • the MOD (maximum operating depth) and the END (equivalent narcotic depth) at the MOD;
  • the ppO2 max that is set;
  • the tank configuration: volume (L), pressure (bar) and total capacity (L);
  • the Edit and Delete buttons.

Adding a mix

Click Add. A dialog opens:

  • Auto label: when on, the name is built from the composition (for instance "21/35" for a trimix). Turn it off to type a name of your own.
  • O2 %: oxygen percentage (5 to 100).
  • He %: helium percentage (0 to 95).
  • N2 %: worked out automatically (100 - O2 - He).
  • ppO2 max: maximum oxygen partial pressure (0.8 to 1.6 bar). The matching MOD and END are computed and shown as you type.
  • Use as bailout gas: marks the gas as available for an emergency way out.
  • Tank configuration: cylinder volume (1 to 50 L) and fill pressure (100 to 300 bar). The total capacity (volume x pressure) is shown automatically.

Confirm with Save.

Add mix dialog with the MOD and END being computed

Editing or deleting a mix

  • Edit: reopens the dialog with the existing values.
  • Delete: removes the mix after confirmation.

Bailout gases

A gas marked "Use as bailout gas" feeds the open circuit bailout simulation in rebreather mode (see CCR mode). On plain open circuit, your decompression gases play that part.

Diluents (CCR mode)

Once rebreather mode is enabled in the Settings, a second list appears: the diluents.

  • Each diluent shows its composition, its MOD (based on a 1.6 bar ppO2 max) and its END at the current setpoint.
  • The diluent in use is highlighted.
  • Adding and editing work as for a mix, but without tank configuration and without the bailout flag. O2 content is limited to 5-21 % and helium to 0-90 %.

At least one diluent must always remain: the last one cannot be deleted.

Oxygen is declared nowhere: a rebreather is dived on two cylinders, a diluent and pure oxygen, which is exactly why a diluent is capped at 21 % O2. Finishing the dive on oxygen is set directly in the CCR Mode block of the Settings.

For the detail of how the rebreather works, see the CCR mode page.