Entering a gas

Add a gas in the Plan step's Gas Mixes section, read the card it produces, and give an open-circuit or rebreather plan the role it will not run without.

The Gas Mixes section holds one Breathing Rates card, then one card per gas, then an Add Gas Mix button. The physics behind each figure is in Depth limits.

The bottom gas of a 45 m dive on 21/35

21/35

Primary

Bottom Gas · Backmount Double

12 L × 2232 bar

TMX 21/35

O₂21%

He35%

N₂44%

Open circuit

ppO₂ ≤1.40 bar

Max depth45.0 m

ppO₂-

Density-

EAD-

Reading a gas card

Four bands:

The role, in small capitals above the mix name, with the cylinder configuration appended: Deco Gas · Stage. The edit, blend and remove controls sit beside it, and a Primary chip marks the gas breathed from the surface.
The composition: O₂, He and N₂ as percentages.
The derived figures: MOD, ppO₂, EAD and Density, plus a switch or drop depth where the gas has one. All are evaluated at one depth, named at the end of the row as @ 45 m.
The cylinder: Tank, Fill and Capacity, and, once the plan is computed, how much you used and what is left.

A gas that breaches a limit at that depth carries the finding on the card itself, always as an amber advisory and never as a red error: a card judges one mix at one depth, and a mix unbreathable there can still be a fine deco gas breathed shallower. Whether the gases you carry cover the dive is judged once, for the whole section, in a banner below the cards. See Warnings.

Adding a gas

Add Gas Mix opens a five-step dialogue. Mixes and roles walks all five.

The roles

Which roles a gas may take depends on the breathing mode. Mixes and roles lists all seven and the oxygen ceiling each carries.

Watch for:

An open-circuit plan needs a Bottom Gas, and a rebreather plan an Onboard Diluent, or the Plan step will not advance. See Warnings.
The gas set must cover the plan’s maximum depth. A red banner below the cards reads “No gas can be breathed at the plan’s maximum depth (45 m). Adjust your mixes or the depth.” on open circuit, or asks for a breathable bailout mix on CCR, and blocks the step just as a missing role does. The amber note “No deco gas configured. Ascent will run on bottom gas / bailout only.” is advisory and blocks nothing.
Changing the breathing mode does not rewrite existing roles, so a plan switched to CCR reads as having no diluent.

Cylinder configurations is the first thing the wizard asks for, and the setting the rest of the gas follows from.