CCR bailout planning

Posted 29 June 2026 · Field Note #20

Bailout: the dive within the dive

Bailout planning answers one blunt question, so let's define it plainly. On a rebreather, "bailout" is the open-circuit gas you carry to breathe your way to the surface if the loop becomes unusable — if a sensor lies, the scrubber fails, or anything else forces you off the unit. Going to bailout means abandoning the efficient recycled loop and breathing from carried cylinders the old-fashioned way, all the way up.

Why this is the hard part: a rebreather's worst case is not a small inconvenience. It is being deep, with a full decompression obligation still owed, suddenly dependent on open-circuit gas that consumes far faster than the loop did. Every breath at depth is compressed by the surrounding pressure, so the same lungful costs several times its surface volume. Add the stops you still must complete, add an elevated breathing rate because you are now a diver dealing with an emergency, and the gas requirement balloons.

So the planning question is precise: do you carry enough open-circuit gas — and the right mixes for each depth — to breathe from the worst moment of the dive, the deepest and longest point, to the surface, completing every decompression stop at a stressed breathing rate? Not the average point. The worst point, because that is where a failure hurts most and your obligation is largest.

The mechanism behind the discipline is simple gas mathematics applied pessimistically. You compute the volume needed for the full ascent and deco from that worst case, confirm each bottle is breathable at the depth you would bail, then check it all against what you are actually carrying. If the honest answer is not a confident yes — with margin — then the dive is too big for the gas you have, and the correct response is to make the dive smaller, not to hope.

The practical takeaway: treat bailout as a real, calculated part of the plan, not a box you wave at on the boat. Carry it, stage it where you can reach it, and size it for the deepest, longest point of the dive. It is the dive within the dive.

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