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ICD violations

What the planner reports when a gas switch fails a counterdiffusion check, and what it does with the schedule afterwards.

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The checks set in the ICD Safety section run at every open-circuit switch on the ascent, and at the switch from the loop to open circuit at a bailout point. A plan carrying no helium has nothing for them to measure and raises none of them.

The schedule is still computed

Every violation is reported at Error severity, and one is raised per failed check, so a single severe switch can produce several. None of them stops the plan: the planner does not refuse the dive, blank the profile or drop the stops. You get the schedule and the failures together, and the judgement stays yours.

Below is that 60 m dive, with the five failures from its one gas change sitting among the rest of the plan’s warnings.

The warnings from a 60 m dive on 18/45 switching to 32 % at 30 m

Dive Warnings

Gas density 5.6 g/L exceeds SPUMS advisory of 5.2 g/L on gas 18/45 (t=24 min)
Gas density 5.3 g/L exceeds SPUMS advisory of 5.2 g/L on gas 32% (t=28 min)
ICD: gas switch 18/45 → 32% at 30m — N₂ fraction increase 31.0% exceeds limit 20.0% (t=28 min)
ICD: gas switch 18/45 → 32% at 30m — He fraction decrease 45.0% exceeds limit 15.0% (t=28 min)
ICD: gas switch 18/45 → 32% at 30m — ppN₂ increase 1.24 bar exceeds limit 0.50 bar (t=28 min)
ICD: gas switch 18/45 → 32% at 30m — ppHe decrease 1.80 bar exceeds limit 0.50 bar (t=28 min)
ICD: gas switch 18/45 → 32% at 30m — EAD mismatch: from 8.8m to 24.5m (diff 15.7m) (t=28 min)
Gas switch to 100% at 6m: ppO₂ 1.62 > 1.6 (t=48 min)

Watch for

  • The checks steer the planner’s own gas choices. It will not pick an ascent gas whose switch fails an enabled check, so a violation almost always comes from a switch depth you set by hand.
  • A bailout switch is checked too, and reports itself with the prefix ICD: bailout switch. Those scenarios are marked and still planned. See Bailout scenarios.

Next

On a rebreather plan, CCR settings is the section that follows. On an open-circuit plan the Plan step is finished: the Review step is where the planner answers.

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