Introduction

**PICK YOUR FAVOURITE TOOL FROM THE MENU**

- MOD - Max Operating Depth
- Best Mix for your target depth
- EAD - Equivalent Air Depth
- NDL Calculator

**EAD DISCLAIMER**

- EAD is an approximation of decompression requirements for nitrox mixes.
- Not all dive tables are recommended for use in this way, while the Bühlmann tables used here are suitable.

**NDL CALCULATOR DISCLAIMER**

- If you're not familiar with decompression theory and their algorithms, then this is not for you. Goodbye.
- No consideration has been given to real-world scenarios, this is theory only.
- No consideration has been given to on-gassing or off-gassing while descending to, or ascending from, target depths.
- This is only intended for illustrative purposes, to give an idea of NDLs at certain depths with certain Nitrox mixes.
- You use this at your own risk. It is not a substitute for dive tables or dive computers.
- The base table is Bühlmann's ZH-L16C. NDL algorithm reference below.

**NDL FORMULA**

Following Erik C. Baker's paper on calculating NDLs, we have the following:

- Definitions:

P = Final partial pressure in a given compartment

Pamb = Ambient pressure at depth

PH2O = water vapor pressure

FN2 = Nitrogen partial pressure at surface

Pi = Inspired pressure, e.g. ambient pressure minus water vapor pressure

Po = Initial compartment pressure

k = time constant for the current tissue compartment

t = NDL for the current tissue compartment

- We start with the basic Haldane equation:

P = Po + (Pi - Po)(1 - e^-kt)

- We rearrange the Haldane equation to solve for time, t:

(P - Po)/(Pi - Po) = 1 - e^-kt

e^-kt = 1 - (P - Po)/(Pi - Po)

- We simplify the equation:

e^-kt = (Pi - Po)/(Pi - Po) - (P - Po)/(Pi - Po)

e^-kt = (Pi - Po - P + Po)/(Pi - Po)

e^-kt = (Pi - P)/(Pi - Po)

- We take the natural logarithm of both sides, to extract t (time):

ln[e^-kt] = ln[(Pi - P)/(Pi - Po)]

-kt = ln[(Pi - P)/(Pi - Po)]

t = (-1/k)*ln[(Pi - P)/(Pi - Po)]

- Lastly, we substitute the surfacing M-value, Mo, for the final pressure, P:

t = (-1/k)*ln[(Pi - Mo)/(Pi - Po)]