An air break interrupts decompression on a high-oxygen gas with a period on a leaner one, to hold down central-nervous-system oxygen exposure over a long stop. The Air Breaks card, in the Decompression section, schedules that cycle for you.
Air Breaks
Once triggered — by CNS% or elapsed runtime — the diver breathes the primary deco gas or setpoint for the deco interval, then breaks for the break duration on the break gas (or a lowered CCR setpoint), repeating until deco clears.
At least one trigger — CNS% or runtime — must be set for breaks to activate.
The fields
- Air Breaks: on or off. A new plan arrives with it off, and the rest of the controls appear only once it is enabled.
- CNS Trigger: a percentage between 0 and 100, starting at 80 %.
- Runtime Trigger: a number of minutes. The regime starts at whichever trigger is reached first, and a plan with neither set never triggers.
- Deco Interval: minutes on the primary deco gas before each break, starting at 20 and greater than zero.
- Break Duration: minutes each break runs, starting at 5, also greater than zero.
- Break Gas: every gas in the plan by name, plus an empty option. A new plan has none chosen.
- Break Setpoint (bar): rebreather plans only, between 0.20 and 1.60. Set it and the break is taken by dropping the loop setpoint rather than switching off the loop, and the break gas is not used.
Once triggered, the diver alternates the deco interval and the break until the decompression obligation clears. Break time is spent at the stop depth on a leaner mix, so the stop grows to compensate.
Which algorithms honour it
Bühlmann ZHL-16C and Thalmann E-L both schedule air breaks, and so does VPM-B, because selecting VPM-B plans the dive on Bühlmann. Hybrid OC, DiveLogic Frontier and Thalmann GF Calibration do not apply air breaks at all; their controls stay visible and editable and change nothing.
Watch for
- A break gas that is not in the plan disables the regime, at Warning severity: “Air-break gas index N is out of range (M gas(es) configured); air breaks disabled.”
- A zero or negative interval or break duration disables it too: “Air-break interval and break durations must both be positive; air breaks disabled.” In both cases the schedule is computed without breaks.
- Break segments appear as separate rows at the stop depth, with the break gas named in the Gas column. Read them in the Advanced view, which puts ppO₂ next to the gas.
Next
Descent and ascent rates is next. Also worth reading: oxygen exposure, for what CNS % counts.