MOD check
How deep a mix you already have may be taken, and what it costs you.
The gas you have
What the analyser read on the tank.
21%
0%
Nitrogen79%
Nitrogen is the balance and is not entered directly. Analysed as Air.
The dive you are planning
Sets which ppO₂ ceiling applies and how much oxygen clock you spend.
min
Used for the CNS estimate. The worst case is the whole dive at the MOD.
°C
Colder gas is denser, which raises work of breathing.
Depth limits
Max depth
30m
Set by END 30 m — not oxygen
Oxygen limit
56m
narcosis binds first
Hypoxic floor
0m
Breathable at the surface
ppO₂ at MOD
0.84bar
What you actually breathe there
What it costs you at that depth
END
30m
Limit 30 m · N₂ only
Gas density
4.8g/L
Limit 5.7 g/L at 20°C
CNS
4.8%
20 min at ppO₂ 0.84
Depth band
| Limit | Depth | Because |
|---|---|---|
| Hypoxic floor | Surface | At or above 18% O₂ |
| Oxygen, working | 56 m | ppO₂ reaches your 1.40 bar limit |
| Narcosis | 30 m | END reaches your 30 m limit |
| Density | 38 m | Density reaches your 5.7 g/L limit |
| Oxygen, deco | 66 m | ppO₂ reaches your 1.60 bar limit |
How to read this
- MOD is floored to a whole metre, END and density are ceilinged — the reported figure is never less conservative than the true one.
- Every value is evaluated at the working MOD, the deepest point this gas may be breathed on the bottom phase.
- CNS is a single-exposure estimate from the NOAA table and assumes the whole bottom time at the MOD. A real profile spends less.
- Need a mix rather than a check? Best mix works the other way round.