END vs EAD

[spatman]

I'm not quite understanding the difference between Equivalent Narcotic Depth and Equivalent Air Depth. Both seem to be calculating the partial pressure of nitrogen and relating it to the narcotic effects at a depth equivalent to that ppN2 using air.

Is the only difference that EAD is used with nitrox mixes and END used with trimix?

[Mattleycrue76]

My understanding is that EAD is used for calculating nitrogen loading/deco whereas END has to do strictly with the narcotic properties of gasses (O2 or nitrogen)

[Joshua Smith]

Matley is on the money. I use the 2 terms interchangeably, myself.

[ljjames]

My understanding is that EAD is used for calculating nitrogen loading/deco whereas END has to do strictly with the narcotic properties of gasses (O2 or nitrogen)

Yes, basically what matt said.

This a hold over from the 'old' days when we did not have nitrox computers and plastic nitrox tables on every corner (there were the NOAA nitrox tables, but not in the pre-printed on plastic mass produced format) We taught students to plan their EAD so that they could just use the recreational air tables they were used to. It also gives folks a nice understanding of what is actually going on, taking some of the 'mystery' out of it. "oh, i see, its simply about reducing the nitrogen'. (keep in mind this was in the early 90's, in an era where mention of Nitrox was banned from DEMA and it was still called the black gas or voodoo gas)

END is narcotic properties of gas as compared to air. Which is a bit amusing to me at times, because we are encouraging shallower and shallower END's and discouraging deep air vehemently, so to a degree the comparison to air as a data point is loosing some of its relevance.

[spatman]

Thanks for the clarification, folks.

My understanding is that EAD is used for calculating nitrogen loading/deco whereas END has to do strictly with the narcotic properties of gasses (O2 or nitrogen)

This makes sense. I wasn't taking the narcotic effect of O2 into consideration.

[kdupreez]

They are not the same and not interchangeable.

EAD is for calculating no decompression limits based on air schedules. for example the PADI nitrox class only provides EANX32 and 36 tables, but if you happened to have 30%, what are you to do? well, to could figure the Equivalent air depth and then use the straight air tables to dive any nitrox mix.

EAD = ((Depth + 33) × FractionOfNitrogen / 0.79) − 33

(eg. EAD for 30/30 @ 100ft = 85ft, so calculate deco on 85ft on air schedules)

END is narcotic depths, you figure out the equivalent depth at which you will have similar narcotic experience if diving non helium mixes..

END = (Depth + 33) × (1 − FractionOfHelium) − 33

(eg. END for 30/30 @ 100ft = 60ft, so you will be as narked at 100ft as air at 60ft)

so, on short, Narcosis versus Decompression limits..

[kdupreez]

a good example of using EAD is actually to do very easy deco calculations on shallow tec dives when diving 32%, 30/30 or even 25/25

we did a dive on waterman's wall today and used the EAD to calculate our deco for the dive on the fly and using like 30/30 backgas and O2 deco gas.

so EAD has a very practical applicability in diving today.

[CaptnJack]

What Koos said.
You calculate a decompression obligation relative to air. On EAN32 you have less of a deco obligation, roughly/rounded to -20% equivalent air depth. So 100ft is really 80ft on an air table. On EAN36 its -25% so 100ft = 75ft on air. This is independent of narcotic depth.

I'm sure you have the formulas in front of you so I won't go through them. But for instance
EAN32 = -20% (of depth) EAD
EAN36 = -25% EAD
30/30 = -20% of depth (EAD), -30% of ATAs for narcotic purposes
21/35 = air for deco purposes, -35% of ATAs for narcotic purposes.

Nitrox uses EAD although some people think that O2 is non-narcotic and subtract that little extra bit of O2 from their narcotic depth. Trimixes have an EAD for decompression table purposes and an END for making assumptions about how you'll "feel" at depth.