Decompression

Repetitive Dive Model

Build a chronological sequence of square-profile dives and see how one named ZHL-16C nitrogen model carries tissue loading through every surface interval.

Build the dive sequence

Enter dives in the order they occur. Each new dive adds its own surface interval, depth, time, and analyzed gas to the same tissue history.

Square profile

Dive 1

Depth

Time at depth

min

Analyzed oxygen

Square profile

Dive 2

Surface interval before dive 2

min

The model applies air breathing at sea-level pressure before the next descent. Enter each break in chronological order.

Depth

Time at depth

min

Analyzed oxygen

All 2 entered exposures remain inside this model's boundary

The displayed margins are model outputs, not a dive plan or a guarantee against decompression sickness.

Dive 1 model24 mAir

Start allowance

28 min

Entered exposure

25 min

Modeled margin

3 min

Limit compartment: #3
End M-value utilization: 95.9%
PPO₂ at depth: 0.72 bar
MOD at PPO₂ 1.4: 56.5 m

Before dive 2: 75 min

Air breathing at 1.01325 bar

M-value utilization: 95.9% → 62.2%

Controlling compartment after interval: #14

Dive 2 model18 mAir

Start allowance

54 min

Entered exposure

30 min

Modeled margin

24 min

Limit compartment: #6
End M-value utilization: 85.0%
PPO₂ at depth: 0.59 bar
MOD at PPO₂ 1.4: 56.5 m

Final modeled state

Compartment #6 is controlling at 85.0% of its GF100 surface M-value. The final GF100 ceiling is at the surface.

Model assumptions

Bühlmann ZHL-16C, nitrogen only
Gradient factors 100/100
Sea-level pressure: 1.01325 bar
Square profiles; time excludes descent and ascent
Air breathing during every surface interval
Initial tissues equilibrated on air at sea level
No-stop allowance rounded down to whole minutes

Tissue loading

\begin{aligned} P_t &= P_i + (P_0 - P_i) \\ &\quad \cdot 2^{-t/T_{1/2}} \end{aligned}

P_t is final tissue nitrogen pressure, P_i is inspired nitrogen pressure, and P₀ is initial tissue pressure. t and T_1/2 are minutes; pressures are absolute bar.

Every result becomes the starting tissue state for the next interval or dive in the entered sequence.

Educational comparison only

This simplified square-profile model omits helium, ascent loading, stops, altitude, personal conservatism, and cumulative oxygen exposure. It is not interchangeable with agency tables or your configured computer. Use the MOD calculator as another educational cross-check.

Related Guides

Decompression & time limits

Surface Intervals and Repetitive Dives

Understand residual nitrogen between dives, how surface intervals restore no-stop time, and the rules for flying after diving.

Decompression & time limits

No-Decompression Limits and Safety Stops

Learn what an NDL represents, compare modelled air and Nitrox limits, and understand how ascent rate and safety stops fit into the plan.

Nitrox & oxygen

Equivalent Air Depth (EAD) Explained

Work out the air depth a Nitrox dive is decompression-equivalent to, and see why EAD never changes your oxygen limit.

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