Reading a deco plan

What this covers

Everything below the scope block in the Deco Planner: the numbers, the graph, the table, the gas cards, and the warnings. All of it recomputes as you edit, so what you are reading always belongs to the plan as it stands right now.

The stats pill

A floating pill sits above the tab bar the whole time you are in a plan. Six cells, divided by hairlines. Tap any of the first five to open an explanation of that number.

Cell	What it is	Notes
RT	Runtime, the whole dive surface to surface: descent, every level, the ascent and every stop. Shown as 54'	Rounded up, so it can read a minute longer than the table’s last Run cell
TTS	Time to surface from where you are on the bottom, the ascent plus every stop. Shown as 45'	This is the “if it goes wrong now” cost
CNS	Central nervous system oxygen toxicity for the dive, as a percentage of the single-dive limit	Yellow at your CNS warning (default 80 %), orange at 100 %
OTU	Oxygen toxicity units, the cumulative pulmonary oxygen exposure	Yellow at your OTU warning (default 300), orange past 300, the recommended single-dive limit, which is fixed and does not follow your warning setting
ρ	The worst gas density in the plan, in g/L	Yellow between your two density thresholds, orange at or above the critical one
Status	Valid, Caution, Unsafe, Invalid or Loading	Tap it to open Plan Issues

A plan with only informational notes still reads Valid, with a blue glyph instead of a green check. Red is reserved for a plan that cannot be dived as written.

The minute prime is deliberate: ' means minutes, and " means seconds in the stop table, so 45' and 45'30" never get confused.

Tap a stat for the explanation

Each stat opens a sheet with the same four parts: the Current value, tinted the same colour as the pill cell; What is this?; Why does this matter?; and, for CNS, OTU and density, a limits table showing the thresholds you are being judged against. Those rows are the real thresholds and nothing else: CNS lists Your warning and Critical, density lists your two configured limits, and OTU lists your single-dive figure beside the 850 daily one. Any warnings that belong to that stat are listed at the bottom.

The density sheet also names what produced the reading, for example TMX 20/25 · 65 m, so you know which gas at which depth is the thick one. On a rebreather it reads Loop.

Diff pills

When you are on a contingency tab or a bailout view, a strip of pills above the graph shows how that scenario differs from the base plan: RT +9', TTS +9', CNS +5%, and NDL -4' for the no-stop time you give up at the deepest level. Green means better, yellow means worse. A pill only appears when the difference rounds to something, and the NDL pill only when both sides have a finite number. Tapping a pill opens the same stat sheet.

The dive profile graph

The graph sits at the top of the results, 120 px tall in portrait and 180 px in landscape. It draws runtime along the bottom and depth down the side.

What you see	What it means
The solid line	Your dive. It is drawn from every segment, including the short hops the table hides, so a stop reads as a flat hold rather than a slope
A red area under the surface	The ceiling: the depth you may not go above at that moment. It is a filled zone, not a line, so the forbidden side is obvious
A translucent yellow band across the middle	The span of time a Stress SRMV burst covers. It is drawn behind everything, because it re-prices gas and never moves a stop
A thick flat blue span at depth	A delay before the ascent, or an air break. Both are real time spent not ascending
Filled dots on the line	Gas switches. Blue for a deco gas, violet for a hypoxic or helium mix
Dashed or dotted ghost lines	Overlays: a variant you switched on, a contingency, or a bailout ascent

The line colour tells you which plan you are looking at: accent for the base plan, orange for a contingency, yellow for a bailout view, or the variant’s own colour.

The graph is not interactive: there is nothing to tap, and no full-screen view to open. Both axes follow your own settings, and the depth gridlines are chosen as round numbers in your unit rather than converted from round metres, so an imperial diver reads 50 ft and 100 ft rather than 98 ft and 164 ft.

The stop table

The table lists every segment of the dive in order. Four columns are always there.

Column	What it holds
Depth	The depth at the end of that segment, in your unit. The last row reads SURF
Stop	How long you hold on that row. Travel rows show -
Run	The cumulative runtime at the end of the row, in bold
Mix	The gas you breathe on that row

Both time columns follow your stop time rounding, so the same plan reads 25', 25'30" or 25'06" depending on the setting, and never mixes the two forms down one column.

The Mix column is written differently on a rebreather. A loop row shows the setpoint, SP 1.4. Once a plan uses a dilout anywhere, every loop row also names its diluent: the onboard one bare, SP 1.4 · 18/45, and a dilout in square brackets, SP 1.4 · [18/30], which is the cue that this row breathes a bailout cylinder as diluent. An open-circuit row that breathes the diluent itself reads 18/45 · diluent. A legend under the table explains the brackets when any are on screen.

How to read a row

A glyph in the first column says what kind of segment it is.

Row	Glyph	What it is
Descent	Orange down arrow	Going down. On a rebreather this can split, so the deep part shows the working setpoint and the shallow part the descent setpoint
Level	Accent filled circle	Time at one of your dive levels
Ascent	Green up arrow	Going up. Short hops between two stops inside one step size are hidden, because the Run column already tells that story
Gas switch	Blue refresh arrows	A change of gas or setpoint, named by the gas you switch to
Forced switch	Red refresh arrows, red gas name	A switch the plan did not choose: the cylinder you were on ran out and the gas named took over. Only on plans set to Switch gas
Deco stop	Yellow dash	A mandatory hold
Delay	Blue timer, with the word under the depth	Your own hold before starting up, from the delay modifier. It is not a deco stop, which is why it is blue rather than yellow
Air break	Blue pause	A break off the high-oxygen gas onto your back gas
SURF	Green up arrow	You are out

Red on this table means something is wrong, which is why the descent arrow is orange: going down is the one thing every dive does.

Switch rows sit where you actually make the change: before descending to a deeper level you switch at the depth you are leaving and descend on the new gas, and on the way up you ascend on the gas you were breathing and switch on arrival.

Optional columns

Four checkboxes under the table add detail. All are off by default and reset when you leave the screen.

Toggle	What it adds
PPO₂	The oxygen partial pressure on each row, two decimals, always in bar. Red below 0.16 or above 1.6, yellow above 1.4
CNS	The cumulative CNS percentage at the end of each row
Remaining Gas	The pressure left in the cylinder that row breathes, walked segment by segment from your fill pressures
Equivalent Mix	On a rebreather only: the open-circuit mix the loop behaves like at that depth, marked ≈ 18/35

With every toggle on, and at a large system text size, the six columns can need more width than a phone screen has. The table then scrolls sideways. Push it left to reach PPO₂ and CNS; the columns keep their full labels and values rather than being squeezed down to fit.

Remaining Gas turns the table into a gauge check for the whole ascent instead of one total at the end. It follows whatever plan modifiers are in force, so a stress burst or a changed rate moves these figures exactly as it moves the Gas Consumption card. On a rebreather it reports the rig’s diluent, including on an open-circuit row that breathes the diluent itself.

When there is no table

What you see	What happened
Calculating...	The engine is working. Nothing is stale on screen while it does
No deco required	The plan surfaces with no mandatory stop
No gases configured	An open-circuit plan with an empty gas list. A rebreather plan still draws the loop schedule
No gas covers depth	You picked a bailout switch depth no gas can be breathed at. The message names the maximum operating depth a gas would need, in your own unit. Pick another depth or add a gas that reaches it
Calculation error	The engine could not produce a schedule. The table is hidden rather than left stale, and the reason appears in Plan Issues

Gas Consumption

One card per cylinder, in this order: the rebreather’s oxygen, then its diluents, then your open-circuit cylinders in your own list order.

Each card is built around a bar. The coloured part is what remains, the grey part is what the dive uses.

• The top row names the gas and shows Used on the right: the pressure and the volume the plan consumes, 140 bar · 1680 L. In cubic feet a figure under 10 ft³ carries one decimal, because a cubic foot is 28.3 L and a whole one is too coarse to size a fill from at the bottom of the range. Bigger figures stay whole.
• Remaining sits under the bar in the bar’s own colour. This is the headline number. It is a gauge reading, so it stops at 0 and never goes negative.
• Short by 34 bar appears in red under Remaining when the plan asked a cylinder for more gas than it holds. That is the number to size a fill from, and it shows whichever When a cylinder runs out setting you are on.
• A cylinder the planner ran down is red. One it handed over from is marked by a dashed red border instead of a solid one, and adds Handed over at 12 m · then 32/0. It can still show a little gas, because the handover happens when the cylinder cannot cover the next segment rather than when the needle hits zero, so expect at most one stop step of gas left in it. Read the dash as “the plan carried on without this bottle”; a solid red card is a bottle the plan ran short on. The two outcomes that are not a handover keep the solid border and really do reach zero: a cylinder with nothing safe to switch to, and one emptied on the bottom, which still gets an Empty at 45 m line because that depth is worth knowing.
• On a rebreather bailout view, the Diluent row adds Loop before bailing: 320 L underneath, the litres the loop already took from that cylinder before you left it.

The four colours are: green above the cylinder’s reserve target, yellow below it, orange under 50 bar (725 psi), and red at zero. The target is your reserve rule from Settings unless that cylinder carries its own, set under Advanced in the gas sheet.

Pressure is the larger figure on every line, with the volume one size down after a middle dot, so divers who think in volume can read it without squinting. The section’s single i explains how every figure is computed, including the rebreather estimates.

Consumption follows your breathing rates. On open circuit the rate follows the cylinder, not the clock: any gas assigned to a dive level is charged at your Working SRMV for every segment it breathes, ascent and stops included, and a cylinder carried only for deco is charged at your Deco SRMV. A rebreather bailout splits the two by phase instead: the leg from the bail point up to the first deco stop is work, so it is charged at the working rate, and everything from that stop to the surface at the deco rate.

Ascent Pressure and Bailout Gas Required

Neither figure is on the Gas Consumption card. Both print in the header of an exported slate, beside Turn Time.

Ascent Pressure is a gauge reading: the pressure your bottom gas should still show as you leave the bottom. It prints on open-circuit plans and on the rebreather loop view, next to the runtime at which you reach it.

Bailout Gas Required replaces it on a bailout view, because there the same slot is a different quantity: the gas the bailout ascent needs in that cylinder, not gas remaining. You do not breathe a bailout cylinder on the bottom, so a “remaining at the turn” reading there would just be the fill pressure.

Neither is the same as the turn pressure in Gas Usage, which is the halfway point of your usable gas on a there-and-back dive. Three different numbers, three different names.

Find the longest bottom time

A timer icon in the Gas Consumption header and Find bottom time in the header menu both open the Bottom time finder. It works the gas question backwards: instead of you typing a bottom time and reading the gas that comes out, it searches for the longest bottom time your plan still supports.

Pick what sets the limit:

• To reserve finds the longest bottom time that still leaves every cylinder at or above its reserve. The reserve comes from your reserve rule plus any reserve you set on an individual cylinder, so the answer always agrees with the colour of the Remaining bar beside it.
• To a TTS finds the longest bottom time whose time to surface fits inside the TTS budget you set on the stepper below the chips. It moves a minute at a time, runs from 5 to 360 minutes, and can be typed straight in. Gas is still checked at the answer and flagged if a cylinder ends up under its reserve, but it does not move the number.

On a plan with more than one level, Which level to extend picks the level the search varies. It starts on the last level, the one the +3 min and +5 min tabs move, which is right for a single-level dive and for a profile that ends at its deepest point. It is often wrong for a multi-level dive: on a 30 m level followed by a shallow one, the shallow level is where you off-gas, so making it shorter makes your ascent longer, not shorter. If the finder cannot get under a TTS budget, point it at the deeper level. Each level is its own question, so switching the picker clears the last answer.

Tap Find and the planner runs your plan at up to fourteen different bottom times and reports the longest one that works, spending a second round of the same size when the answer turns out to be a window. The result names the difference against your planned time (“6 min more than planned”), the time to surface at that time, and the cylinder that reaches its reserve first. The time to surface is written the way the deco table writes one and follows your stop time rounding, so the same TTS reads 41'42", 41'30" or 42'. The bottom times are whole minutes: the answer itself, the difference against your planned time, the ends of a window and the value Apply writes are all rounded to the nearest minute. Apply writes the bottom time onto the level you picked and changes nothing else.

The finder answers the tab you are on. On Base Plan that is your plan as written. On a contingency tab the search runs your plan with that tab’s lost gases, extra depth and extra time, so the answer is the bottom time you can plan and still meet the limit if that scenario happens. Every label names the tab, “Bottom time to reserve under +5 min: 28 min”, so an answer can never be mistaken for the plan’s own figure. Switch tabs and the finder starts with nothing solved, because each tab is a different question.

Some levels answer with a window. On a level shallower than the ones before it you are off-gassing, so a longer stay gives a shorter ascent, and the times that meet a budget are “at least N minutes” rather than “at most”. The finder says “From 7 min” with the time to surface there, then where the window closes, either because your gas runs out or because the ascent grows back over the budget. Apply takes the lower end, the smallest change that meets the budget. If the gas gives out before the budget is met, the sheet says so in red with both numbers.

When nothing works it says what it measured rather than just “no answer”: the shortest time to surface the plan can reach, or the cylinder that finishes short and by how much. When its own probes show that staying longer would give a shorter ascent, it says so and points you at a deeper level.

The answer is tied to the plan it was solved for. Change a fill pressure, a gradient factor, a gas or a level and the number disappears rather than sitting there looking current. While it is valid, it also prints as a quiet line under the gas bars, and the timer icon carries a small dot.

The finder is not offered on a rebreather plan, or on a bailout view. On a rebreather the thing that ends the dive is usually scrubber duration, which Dive Kit does not model, so a gas-only number would look like a complete answer to a question it has not answered. On a bailout view the gas figures describe an open-circuit ascent from your switch depth, and what counts as enough gas there is set by the bailout checks rather than by your reserve rule.

In the sheet itself, the one line under the Find button says the same thing in short, and the (?) beside it opens the full version.

What the warnings mean

Warnings appear as cards above the plan and in the Plan Issues sheet, which the status cell opens. Every one has a bold title saying what is wrong and a detail line saying why, with the numbers. They are sorted worst first, and pressures are printed in your own unit.

Four severities, and the difference matters:

Severity	Colour	Meaning
Invalid	Red	The plan cannot be dived as written
Critical	Orange	Urgent, but the plan still computes
Warning	Yellow	Worth a second look
Info	Blue	A note. The plan is fine

Critical and invalid

What it says	What raises it
gas: insufficient gas	The dive needs more gas than that cylinder holds. The detail gives the shortfall
gas: critically low gas	The plan finishes that cylinder between 0 and 50 bar (725 psi). This floor is absolute and no reserve rule moves it
gas runs out at depth, nothing to switch to	With switching on, the cylinder emptied and nothing you carry is safe to breathe there. It also covers a handover that would be a dead end: if the gas taking over would fall below your Minimum PPO₂ higher up and nothing else you carry is safe there, the planner does not make the switch and plans that cylinder the way Show shortfall would
gas runs out at depth before the ascent	The cylinder emptied during the bottom phase, so the deco was planned without it
CNS n%: critical oxygen toxicity	The dive reaches 100 % of the single-dive CNS limit
OTU n: pulmonary O₂ exposure beyond the single-dive limit	Cumulative oxygen exposure passes 300 OTU, the recommended limit for one dive. That figure is fixed and does not follow your OTU warning setting. The daily figure is 850, which is what the stat sheet lists beside it and which nothing warns on
gas exceeds MOD depth	The oxygen partial pressure on a level goes past 1.6 bar, the universal ceiling
Gas density critical	A breathed gas is denser than your critical threshold, default 6.2 g/L
Severe hypoxia risk	A breathed PPO₂ falls below 0.16 bar, at the surface or at a level
No gas assigned at depth	A level points at a cylinder that is not in the plan, so its checks were skipped. Set the level to Auto or pick a gas
Hypoxic loop: setpoint n bar	A rebreather setpoint below 0.16 bar
No bailout gas depth	Nothing you carry is breathable at the last planned depth, or nothing covers the deepest point of the dive
Not enough bailout gas in gas	A worst-case bailout from the last planned depth needs more than that cylinder holds
Not enough gas in gas for dilout plus bailout	The same cylinder feeds the loop as a dilout and the bailout plan, and the two together do not fit
Bailout leaves gas below its reserve	The bailout fits but finishes under the reserve you typed for that cylinder
GF high raised to n	Your GF High could never surface the plan, so the engine used the lowest value that can. The schedule shown is not the conservatism you asked for
Depth exceeds maximum limit	The profile goes past 200 m (650 ft), which the model does not compute beyond
Ascent pressure exceeds start pressure	The ascent needs more gas than the cylinder started with
Calculation error	The engine could not produce a schedule at all

Cautions

What it says	What raises it
gas: below reserve	The plan finishes that cylinder above 50 bar but under its reserve target. The detail names the target it judged you against
gas runs out at depth	With switching on, the cylinder emptied mid-deco and another gas took over cleanly, carrying you to the surface. The detail names both gases and how much more of the first would have finished. A handover that still leaves that cylinder short is critical rather than a caution
CNS n%: elevated oxygen toxicity	CNS reaches your warning threshold, default 80 %
OTU n: elevated pulmonary O₂ exposure	OTU passes your warning threshold, default 300
gas exceeds MOD depth	A level’s PPO₂ goes past that gas’s own band cap but stays under 1.6 bar
Gas density high	A breathed gas passes your warning threshold, default 5.2 g/L
END exceeds n limit	A level’s equivalent narcotic depth passes your threshold, default 30 m (100 ft)
Low PPO₂	A breathed PPO₂ falls below your Minimum PPO₂ setting, default 0.18 bar, without reaching the 0.16 critical floor
ICD risk: gas switch depth	A switch at 20 m or deeper raises nitrogen while cutting helium past Burton’s 1:5 rule. Consider an intermediate step-down
Level n time is too short	With Include travel in level time on, the level’s time is shorter than the travel needed to reach it
No bailout gases configured	A rebreather plan with no open-circuit gas at all
Low loop PPO₂	A rebreather setpoint below your Minimum PPO₂ setting

Notes

What it says	What raises it
Hypoxic gas: gas	The mix is too lean to breathe at the surface. The note gives its minimum operating depth
HPNS risk / Severe HPNS risk	A helium mix at 80 m or deeper, or 120 m or deeper
Hypoxic diluent	The rebreather diluent is hypoxic near the surface, so do not flush or bail out to it shallow
Diluent exceeds setpoint below depth	Past that depth the diluent’s own PPO₂ is above the setpoint, so the unit cannot hold the target
Setpoint unreachable	A deco setpoint that cannot be reached above a given depth on your diluent. The loop runs at the achievable value instead

Behaviour and limits

• Every figure here is recomputed from the inputs. Nothing is cached across an edit, and a stale plan is replaced by a banner offering to recalculate rather than left on screen.
• The graph, the table and the gas cards all read in the units you set. PPO₂ is the one exception and is always in bar.
• The optional table columns are not saved with the plan and not carried into the export sheet, which keeps its own choices.
• Gas figures assume the fills you typed and the breathing rates you set. They are the least certain numbers on the screen.

Related

• Deco Planner is the tour of the whole tool.
• Contingencies and plan modifiers explains the tabs and rates these figures follow.
• Hazards beyond decompression covers the physiology behind the density, narcosis and hypoxia warnings.
• Printing and exporting a slate turns this table into something you can take in the water.