Contingencies and plan modifiers

What this covers

A plan is one dive. The scenario tabs under the inputs are the other dives you might end up doing: three metres deeper, five minutes longer, or without the stage you dropped. This page covers those tabs, how to build your own, and the four plan modifiers that change how much gas a scenario costs and, in one case, how long it takes.

Everything here is a planning aid. None of it makes a bad situation survivable; it tells you what the situation would cost.

The built-in scenarios

The planner generates these without being asked, and computes each one as a full plan.

Tab	What changes
Base	The plan as you wrote it. The tab you start on
+3m, +5m	The deepest level goes 3 m or 5 m deeper. Imperial divers get +10ft and +20ft
+3min, +5min	The last level runs 3 or 5 minutes longer
+3m/+3min, +5m/+5min	Both deltas together, on the deepest level
Lost gas	One cylinder is gone. One tab per losable cylinder

The depth-versus-time asymmetry is deliberate and matches what the engine has always done: extra depth belongs to the deepest part of the dive, extra time to the part you were on when you overstayed. On a profile whose deepest level is not its last one, that is two different levels.

A lost-gas tab is generated for any cylinder that no dive level breathes once Auto has resolved the plan, and that is not marked Exclude from Deco. In practice that means your stages and deco bottles. Your bottom gas never gets an automatic tab, because losing it is not a deco problem, it is a different dive. Build it by hand if you want to see it.

There is no automatic “lost every deco gas” tab either. Combinations are what the custom builder is for.

Tabs sort in a fixed order: Base, then your custom scenarios newest first, then the built-ins, then the lost-gas tabs.

Reading the tabs

A tab carries more than its name.

What you see	What it means
A second line like +7min	How much longer this scenario’s time to surface is than the base plan’s. Green when it is shorter, yellow when longer. Hidden when the difference is zero
A red warning glyph and border	The engine had to raise this scenario’s GF High to make it surface at all. The schedule on that tab is not the conservatism you asked for
A small dot	This tab carries plan modifiers of its own that actually change something
A ✕	A custom scenario. Tapping it deletes the scenario immediately, with no confirmation
A spinner chip at the end	The planner is still computing the rest of the scenarios

Switching tabs changes everything below it: the graph, the table, the gas cards and the warnings all describe the tab you are on. The inputs above do not change, because every scenario is the same plan seen differently.

What losing a gas means

By default, losing a gas means you never carried it. The planner removes that cylinder and replans the whole dive without it, descent and bottom included.

If a level was breathing the lost gas, that level moves to the best surviving legal gas at its depth, chosen by the same rules Auto uses: the mix has to sit inside its PPO₂ band at that depth, pass the density check, and make sense on the way down. The substitute shows up in the stop table and in the gas cards, so the replan is never silent.

That models “I got to the boat and the bottle was empty”. It does not model “my back gas failed at 23 m (75 ft)”, because it also takes the gas off the descent and the bottom, so the plan asks for far more gas than the real failure would. For that, set a failure point.

Build a custom contingency

Tap the accent-coloured + at the start of the scenario tabs. The builder saves when you dismiss it, and a draft with nothing selected and no deltas is thrown away rather than saved as an empty scenario.

Name is the first field, optional, up to 24 characters. It replaces the derived label on the tab and in your exports, so a tab can read “Deep stage gone” instead of the parts it was built from. It is first because the keyboard would otherwise bury it.

Lost gas lists every cylinder in the plan, including your bottom gas, as tappable cards. Pick as many as you want to lose.

Fails after: when the gas is lost

Once you have selected at least one gas, and if the plan has more than one level, a Fails after row appears.

• From the start is the default. The cylinder was never carried, which is the meaning every scenario had before this option existed and what every older plan and share link still means.
• After (2) 30 m, one chip per level, keeps the cylinder for every level up to and including that one and bills the gas you actually breathed from it, then takes it away. Later levels move to a surviving gas, and the ascent can never switch back to the failed cylinder.

The second form is the one that answers “if my back gas goes at 23 m, does the pony get me up?” without hand-building a second plan.

The chip for the last level is disabled when the gas you selected is the gas that level is already breathing. Losing it only after the last level would change nothing, because you are still on it when the ascent begins, so the scenario would quietly hand you the base plan under a contingency label. Use From the start for that case, or set the failure point a level earlier.

Extra depth or time is the second section. Adjust which level picks the level to change, defaulting to the deepest one, and is hidden on a single-level plan. Depth change and Time change are both signed: depth moves ±30 m (±100 ft) and time ±60 minutes, and a negative value makes the level shallower or shorter. The result is clamped so a level never drops below 1 m or 1 minute. Two live lines under the steppers show the level as it stands and as it will be, so you can see the change before you commit it.

Modifiers is the last section, collapsed, and prefilled with what this scenario would inherit. Its header says what it is holding, so you can tell there is something inside without opening it. Setting rates here means a scenario can be created complete in one pass.

A custom scenario cannot be edited afterwards. Delete it and build it again: it is a handful of taps, and an editable scenario would need a second set of rules for what “edit” means to a tab that other things now reference.

CCR views

On a rebreather plan a second row of chips sits under the scenario tabs: CCR for the loop ascent, Full Bailout for an open-circuit ascent from the bottom, and Bailout at depth for leaving the loop part way up. Add depth opens a sheet with the standard stepper, so you can nudge the switch depth a metre at a time or type it, and closing the sheet adds the chip.

Views and scenarios are different axes. A scenario changes the dive; a view changes how you get out of it. You can combine any of one with any of the other. See CCR diving for what each view computes and how bailout gas is checked.

Plan modifiers

Under the scenario tabs sits one quiet line: Modifiers · default. It means this tab is running on the numbers it would use anyway. Tap it to open the Plan Modifiers sheet. If you never open it, nothing else about the planner changes.

Once something is set, the line lists it in yellow and drops the word “Modifiers”, because the tune icon beside it already says what the line is: Work 25 · Stress 45 × 5 min · Delay 2 min. It stays pinned to the top with the tabs and the view chips as you scroll.

The four rows

They sit in the order they happen on the way up.

Row	Range	What it does
Working SRMV	1 to 200 L/min (0.05 to 7.1 ft³/min)	Your working breathing rate. On open circuit it is charged to any cylinder a dive level breathes, for the whole dive. On a rebreather bailout it covers the bail point up to your first deco stop
Stress SRMV	Same range, plus a window	A burst of hard breathing. It overrides the phase rule inside its window
Delay before ascent	0 to 60 min	Time you hold at depth before starting up: sorting a problem, or swimming out to an exit
Deco SRMV	Same range	Your deco rate. On open circuit it is charged to cylinders carried only for deco, at any depth. On a rebreather bailout it covers the first deco stop to the surface

The stress row sits between the two rates because that is where it sits in the dive. Working covers the climb to your first stop, the burst overrides whichever part of that climb it lasts for, and Deco takes over from the first stop.

A stress burst starts the moment bottom time ends, or on a Bailout at depth view the moment you leave the loop, and runs either for a Duration you set in minutes (1 to 60) or all the way to the surface. Each row prints a line of your own numbers under its label: which depth the rate covers to, where the window starts, and what the burst or the hold costs in litres and bar on which cylinder.

What each one moves

Three of the four are gas-only. They re-price the dive and leave every stop where it was, which is exactly what you want from a what-if about breathing.

The delay is the exception, and it is not a what-if at all. It is real time at depth, so it loads tissues, accrues CNS and OTU, and lengthens your runtime, your time to surface and your stops. It shows on the profile graph as a flat blue span and in the stop table as a row labelled Delay with a timer glyph, so it can never be read as a deco stop. On a rebreather it runs on the bottom setpoint you are actually breathing, so three minutes of hold costs exactly what three more minutes of bottom time costs. On a bailout view it happens at the bailout depth on the bailout gas.

Which tab a modifier belongs to

Modifiers are remembered with the plan and scoped by where you set them. The sheet states the scope at the top, under Applies to.

• Open it on the Base Plan tab and the values belong to the whole plan. The two rate rows there are your per-plan settings, the same ones under Advanced › Gas Consumption, with the same override dot and the same reset. Each of the two says so under its label, with a link glyph: “Same as Settings › Advanced › Gas Consumption. One setting, two places.”
• Open it on a contingency tab and they belong to that contingency alone.

There is no third level. Open the sheet while you are looking at a bailout view and you are editing the tab that view sits on, which is what the Applies to line says. The view still decides where a modifier bites, not which one applies.

On a contingency tab the first chip of every row reads Plan, and the row spells out what that is worth: “Plan: 25 L/min”. On the Base Plan tab the equivalent line reads “Your defaults: 20 L/min”, because that is the level the plan itself falls back to. You never have to switch a row to Custom to find out what it was using.

A row also says where its number came from, so a value you inherited is never mistaken for a default:

• A filled dot beside the title and the line in accent: you set this on the tab you are looking at.
• A hollow dot and the line in grey: the row is on Plan, but the base plan changed that value. It is inherited, and it is not a default.
• No dot: the row is on Plan and the plan is at your own Deco Planner defaults.

The stress row has a third state, Off, for the case Plan cannot express: no burst on this tab even though the plan has one. It travels in a share link as its own value, so a contingency you deliberately left calm does not pick the base plan’s burst back up on your buddy’s phone.

The reset button at the top of the sheet clears exactly the tab you have open. It reads Reset to defaults on the Base Plan tab and Reset to plan on a contingency. On the Base Plan tab that puts the two rates back to your Deco Planner defaults and removes any burst and delay; on a contingency it clears that tab so every row reads Plan again. It is greyed out when there is nothing to clear.

On a rebreather plan the two rate rows stay visible on every view, labelled as open-circuit gas rates, with a note on the loop view: they do nothing to the loop, and they are what the bailout views and the bailout gas check run on. They disappear only on a pure loop dive with no bailout cylinders and no open-circuit level, where they would do nothing at all.

Behaviour and limits

• A contingency is computed from your plan’s own settings. Changing a gradient factor or a rate in the settings changes every tab at once; only modifiers are scoped to one tab.
• The NDL tag on a level row always describes the base plan. A contingency’s cost in no-stop time shows as a difference pill instead.
• The bottom time finder answers the tab you are on, and its answer does not follow you to another tab.
• A slate export prints the scenario’s name in the card title, and any non-default modifiers in the header stats line, so a printed contingency can never be mistaken for the base plan.
• Deleting a custom scenario is immediate and cannot be undone.

Related

• Deco Planner is the tour of the whole tool.
• Reading a deco plan explains the figures a scenario changes.
• CCR diving covers the bailout views these tabs combine with.
• Printing and exporting a slate puts two scenarios on one card.

When a contingency runs your bottom gas dry

If a contingency is deep enough or long enough that your bottom gas is gone before the ascent even starts, the planner stops trying to route you home on what is left. With Switch to the next gas it would otherwise drop that cylinder from the plan and run the whole shallow decompression on your deco gas, which produces a tidy-looking schedule for a dive you cannot do, and can even read as shorter than the contingency one step shallower.

Instead the plan falls back to the Stay on it, show the shortfall answer for that cylinder: it keeps breathing it, the gas card shows how many bar short you are, and a red warning says the cylinder ran out before you left the bottom. That is the question worth answering at that point, which is how much more gas the contingency needs, not which order to breathe the gas you do not have. Cylinders that run out during the ascent still hand over as usual.