Deco gases must be checked (✓) to be used by the algorithm. The richest checked gas within PPO₂ limits is selected at each depth.
CCRClosed Circuit Setup
SetPoints and bailout planning for this plan
SETPOINTS
Surface SP: used surface → switch depth on descent, and from switch depth → surface on ascent. Bottom SP: used below switch depth. Deco SP: used at all deco stops. Per-segment SP overrides bottom SP for that segment.
BAILOUT PLANNING
App validates that your personal bailout cylinders are sufficient for your own OC ascent from maximum depth. The volume is for one diver only — no gas is reserved for donating to a teammate whose bailout fails.
⚠ Group bailout selected. Gas sufficiency is the responsibility of the dive team as a whole. AeroPlus Deco does not validate group gas totals. Ensure surface support and pre-staged deco stations are confirmed before the dive. Bailout cylinders below are listed for team reference only.
For chest-mount units where the back cylinder feeds the loop and also serves as bailout. The reserve below is held back for diluent already used (mostly on descent) and is excluded from the bailout gas available.
Cylinders below are bailout OC gas — not used by the deco algorithm on CCR.
About GF99: GF99 is the percentage of the M-value currently in use across all tissue compartments. A negative value means you are on-gassing. Zero is equilibrium. A positive value means you are off-gassing. The recommended target during deco stops is approximately 50% of your GF(hi) setting (shown as the blue dashed Target GF99 line).
Rock bottom & TTS
Rock bottom reserve: Minimum bottom gas for 2 divers at emergency SAC. With a deco gas: from max depth to the first switch depth, including the gas switch pause. With no deco gas: the whole ascent to the surface, including every decompression stop, since back gas carries the full obligation.
Ascent trigger
Start your ascent when either your dive computer shows TTS ≤ your target, or your gas reaches the minimum reserve — whichever comes first.
min
Gas plan
Used
Reserve
Unused
Cylinders
No.
Mix
Size (ℓ)
Usage (bar)
Used (ℓ)
Limits
Depth (m)
Mix / SetPoint
Density (g/ℓ)
PPO₂
Gas density: Values calculated at 15°C reference temperature. On CCR the loop gas is recirculated and slightly warmed by the scrubber — density is calculated for the loop gas composition at depth, not raw diluent. Loop SetPoint is the planned loop PPO₂ used by the algorithm. Diluent PPO₂ and Diluent EAD are calculated for the raw diluent at that depth — what you'd see on a diluent flush, solenoid failure, or OC bailout to diluent.
Plan optimizer OC
Advisory suggestions computed from the calculated plan and your configured limits (PPO₂, gas density, isobaric counterdiffusion, rock bottom). Nothing is changed automatically — adjust your gases or profile only if a suggestion makes sense for your dive.
Checklists
Checklist
Checklists Responses
Edit checklist
Add cylinder
Add segment
Bottom time includes descent time to this section.
Dive configuration
Mode — OC & CCR
CCR mode
Enable Closed Circuit Rebreather planning. The algorithm uses setpoint-based O₂ fraction. No deco gas switching occurs on CCR — all non-diluent cylinders are bailout gas.
Diluent O₂ from target PPO₂
Best-mix diluent. Off = fixed 10% O₂. On = diluent O₂ set so its PPO₂ at depth is about 1.0 ata.
Bailout switch time
Mandatory pause when switching to bailout gas (OC). Added to gas requirement.
2 min
Diluent, setpoints and bailout mode are on the main planning page when CCR mode is active.
Algorithm — OC & CCR
Model
The type decompression model to use.
ZHL-16C-GF
Gradient factor
GF Low/High change the conservatism used by the decompression model.
30/85
Auto-set GF Low
Automatically sets GF Low to match the first gas switch depth (Andy Davis method).
Environment
Units
Depth, pressure and volume throughout the app, and the decompression stop grid.
Metric
⚠ Imperial support is experimental. Depths, pressures, volumes and the 10 ft stop grid have been converted throughout, but this mode is new and less tested than metric. Cross-check any plan against a desktop planner before diving it, and report anything that still reads in metres, bar or litres.
Salinity
Saltier water is heavier and increases pressure at depth.
Salt
Altitude
The altitude of the water surface at which the dive is taking place.
0 m
Diver & Gas
Ascent speed
The speed at which the diver is planning to ascent to stops or the surface.
10 m/min
Deco ascent speed
Speed ascending between decompression stops.
3 m/min
Descent speed
The speed at which the diver is planning to descent to planned bottom sections.
2 m/min
Gas usage OC
SAC/RMV at 1 atm. Used for descent, bottom time and travel-gas switches — and for the ascent portion of the reserve after the elevated-SAC window.
20 l/min
Gas usage emergency
Panic SAC/RMV. Used only for reserves (rock bottom and CCR bailout), never for the planned dive.
30 l/min
Gas usage deco OC
Used for deco stops, ascents between stops, gas-switch pauses and the final ascent — and for the deco portion of the reserve after the elevated-SAC window. Usually lower than normal SAC.
10 l/min
Elevated SAC for first minutes OCCCR bailout
On: the reserve uses the panic SAC only for the first minutes of the emergency, then each phase reverts to its own planned rate — Gas usage on the ascent, Gas usage deco on stops, inter-stop ascents and gas switches. The elevated minutes are spent in order from the start of the emergency, so they may run out part-way through a stop. Off: panic SAC for the entire reserve — to the first gas switch for bottom gas, to the surface for CCR bailout. Lowers the reserve when on.
Elevated SAC duration OCCCR bailout
Minutes billed at the panic SAC before each phase falls back to its own planned rate.
2 min
Decompression
Last deco stop
6 m
Max PPO₂ OC
1.4
Max deco PPO₂ OC
1.6
Use 2025 revised CNS limits
Compute CNS against the 2025 NOAA workshop guideline (Hoyt et al. — 240 min at a 1.3 ata setpoint) instead of the conservative 1991 limits. Applies at PPO₂ ≤ 1.3; richer gases keep the 1991 limits. See the references.
Gas switch time OC
1 min
Min surface PPO₂ OC
0.18
Travel gas reserve OC
50 bar
Switch deco gas at MOD OC
When enabled, switch to the richest available deco gas immediately upon reaching its MOD during ascent.
Multi-level
Use deco gas between sections
When ascending between multi-level sections, allow automatic use of deco gas.
Contingency plan
Deeper
3 m
Longer
3 min
Defaults
Save as default settings
Save the current plan's settings as the starting configuration for all new plans.
Best mix for depth
Depth
metres
PPO₂
ata
Trimix
Include helium in the mix
Limit gas density
Target ≤5.2 g/ℓ; goes hypoxic if depth requires
Target EAD
narcotic depth (m)
Result
Best mix
O₂/He ratio
—
MOD
at 1.40 ata
—
N₂ fraction
balance gas
—
Diluent flush at depth
loop PPO₂ after a flush
—
How it works (OC): Best O₂% = PPO₂ ÷ absolute pressure at depth. For trimix, helium replaces N₂ to match your target narcotic depth (EAD).
MOD / ENDCCR DILUENT
O₂
percent (%)
He
percent (%)
Mix21/0O₂/He
Depth
metres
PPO₂ limit
Setpoint
CCR loop PPO₂ (ata)
Results
MOD
max operating depth
—
PPO₂ at depth
—
EAD
N₂ narcotic — He inert — used for planning
—
END
N₂ + O₂ narcotic (GUE method)
—
EADD
N₂ narcotic — density based
—
Gas density
warn >5.2 ● limit >6.2 g/ℓ
—
Loop gas density
in the breathing loop at the setpoint
—
EAD — He inert, O₂ non-narcotic (most agencies). END — O₂ narcotic (GUE). EADD — density-equivalent depth.
CCR loop: the entered mix is your diluent. At the setpoint the unit adds O₂, so the loop O₂ fraction = setpoint ÷ absolute pressure, with the diluent’s He/N₂ scaled to fill the rest. Loop gas density is what you actually breathe — it can sit above or below the diluent’s, since O₂ is heavier than the He it displaces.
Setting
Setting
Gradient factors
GF Low controls conservatism at the deepest stop. GF High controls conservatism at the surface.
Save data
Copy this JSON and save it somewhere safe.
Load data
Choose a saved .json file or paste JSON data below.
Import plan from link
Paste the shared plan link or message below. The plan will be added as a new plan alongside any you already have.
Import or restore
Share or back up
Gas Blending
Top-up result
What mix do you get if you top up an existing fill with another gas? Pressures only — cylinder size and temperature don’t change the result.
Cylinder
Current fill
Target mix
Top-up gas
Gas analysis depth
Heat compensation
Overfill for cooling
Gas heats during filling — overfill to compensate.
Slow fill ≈ +5–15°C · Fast fill ≈ +20–40°C
Partial pressure blending: He first → pure O₂ → top-up gas to reach final pressure. Always fill in order: He → O₂ → top-up.
About
AeroPlus Deco
Technical dive decompression planning.
AeroPlus Deco is a technical dive decompression planner for open-circuit and closed-circuit rebreather diving, built on the Bühlmann ZHL-16C-GF algorithm. Developed by Magnolia Blossom BV, Doesburg, The Netherlands.
Core algorithm
✓ Bühlmann ZHL-16C with gradient factors (GF Lo / GF Hi) ✓ Optional Auto GF Low tied to deepest deco-gas switch ✓ Trimix (N₂ + He + O₂) with helium tracking ✓ Fresh / salt water and altitude compensation ✓ Configurable ascent and descent rates ✓ Full metric or imperial units — depth, pressure, volume, SAC
Open circuit
✓ Multi-gas planning with automatic deco-gas switching ✓ Travel gas with calculated switch depth ✓ Hypoxic bottom-gas safety check ✓ Rock-bottom (minimum gas) reserves per cylinder ✓ Gas density warnings (5.2 / 6.2 g/ℓ thresholds)
Closed circuit (CCR)
✓ Loop setpoints: surface / switch-depth / bottom / deco ✓ Per-segment setpoint override ✓ Diluent / Oxygen / Bailout cylinder roles ✓ Diluent usable as OC bailout, with configurable reserve ✓ Bailout sufficiency check (independent or group) ✓ Loop density and diluent PPO₂ / EAD validation ✓ O₂ use is deliberately not calculated — monitor your supply in the water
Safety outputs
✓ CNS% and OTU oxygen-toxicity tracking ✓ TTS (time to surface) with ascent trigger guidance ✓ Tissue saturation (GF99) chart ✓ Critical warnings reviewed before diving
Planning tools
✓ Multi-plan workflow with tissue offgassing between dives ✓ Contingency plans (deeper / longer) ✓ Best mix calculator (OC + CCR diluent) ✓ MOD / EAD / END + gas density calculator ✓ Partial-pressure gas blending with heat compensation ✓ Checklists — packing, CCR assembly and pre-dive, with positive/negative pressure tests, timers and a signed-off record of each run
Sharing & backup
✓ Plain-text briefing for Messages / Mail / Notes ✓ Print-ready graphical report (PDF via Safari) ✓ Editable plan link — buddy opens in any browser ✓ JSON backup & restore of all plans ✓ Checklist export / import, and restore of built-in checklists ✓ Installable as a home-screen app, works offline
Documentation
The full manual covers decompression concepts, planning workflows, CCR setup, calculator details, and FAQ.
✓ CNS oxygen toxicity limits — the optional 2025 revised limits follow Hoyt JT, Murphy FG, Pollock NW, Kernagis D, Bird N, Menduno M, Bright J, Mitchell SJ. Revised guideline for central nervous system oxygen toxicity exposure limits when using an inspired PO₂ of 1.3 atmospheres. Diving and Hyperbaric Medicine 2025;55(3):262–270. The default limits remain the conservative 1991 NOAA tables; switch in Settings → Use 2025 revised CNS limits.
⚠ Planning calculator only. AeroPlus Deco performs decompression and gas calculations to help you prepare a dive plan before entering the water. It is not a dive computer and cannot be used during the dive itself — divers must use a certified dive computer for in-water decompression management. Always verify calculations against a second planning source before relying on them.
Help & feedback
Found a bug, have a feature request, or just want to share how the app is working for you? Drop a quick email — no account needed.
Send feedback
Opens your mail app with app version and browser info already filled in. Just add your message and hit send.
1. Tap the Share button in Safari 2. Tap "Add to Home Screen" 3. Tap Add
INSTALL ON ANDROID
Chrome shows an "Install app" banner — tap it, or use ⋮ menu → Add to Home Screen.
INSTALL ON DESKTOP
Look for the install icon in the address bar (Chrome/Edge) and click Install.
Why install?
✓ Launches from home screen ✓ Full screen — no browser bar ✓ Works fully offline ✓ Plans saved locally on your device
USING IT OFFLINE (e.g. ON A BOAT)
AeroPlus Deco runs fully offline — no internet or mobile signal needed, so it works on a boat or anywhere out of coverage. The one thing to do first: start the app up while you still have a connection, so the latest decompression algorithms load onto your phone. Then keep it running in memory — leave it open in the background rather than force-quitting it — and it will plan dives normally with no coverage at all.