Discussion about EAD & END terminology

Henrik Brautaset Aronsen subsurface at henrik.synth.no
Mon Dec 9 23:51:45 UTC 2013

On Tue, Dec 10, 2013 at 12:15 AM, Salvador Cuñat
<salvador.cunat at gmail.com>wrote:

> Attached is a simple patch that will do the work. No changes on strings
> and tried on EAN and TRIMIX test dives.
> Would need a test run with CCR dives but it's far beyond my
> posibilities, and I expect it would work well.

I'm not able to test until tonight but something looks wrong with this

1) "EAD --> Equivalent Air Depth, considering N2 and He if diving trimix"

This is just wrong.  You are talking about Helium and Trimix in the context
of EAD, which is weird.  EAD is mainly used to show the depth as if you
where diving on air, when doing Nitrox dives.  That way I can use Air
tables when diving with Nitrox.

2) "Equivalent Narcotic Depth, considering both N2 and O2 narcotics."

The description is better, but the calculation looks off somehow.  The role
of END is to take into account the narcotic content of the gas, when doing
Trimix dives: (pO2 + pN2) == (1 - pHe).  It is used to show how narcotic my
trimix gas at a given depth is, compared to when diving on air.  If you
look at my previous calculation:

   The END (Equivalent Narcotic Depth) at 57 meters is (1 - fHe) x ATA = (1
- 0.45) x 6.7 = 3.7 ATA = 27 meters

That means that when diving with 18/45 to 57 meters, I will not get more
narked than if I was diving with air to 27 meters.  Good stuff.

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