joorev - Nitrox Toolkit
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)]