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- MOD - Max Operating Depth
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- EAD - Equivalent Air Depth
- NDL Calculator
- 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.
Following Erik C. Baker's paper on calculating NDLs, we have the following:
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)]