Equivalent nitrogen depth

[rjack321]

Whan I see "END" I read "Equivalent Narcotic Depth," and figure that at (100% - He%) * ATA. In other words, both Nitrogen and Oxygen count full measure for loopiness.

This is how mine is guesstimated.

 

[Meng_Tze]

It depends which agency you were trained with.

Not sure which one has a different definition.

 

[Rick Murchison]

The NOAA diving manual states:
"16.3.1.2.4 Equivalent Narcotic Depth
... since oxygen has some narcotic properties, it is appropriate to include the oxygen in the END calculation when using trimixes (Lambersten et al. 1977,1978). The non-helium portion (i.e., the sum of the oxygen and the nitrogen) is to be regarded as having the same narcotic potency as an equivalent partial pressure of nitrogen in air, regardless of the proportions of oxygen and nitrogen. ..."
Looks good to me
--
So, which agency just looks at Nitrogen? (I could guess, but ...)
Rick

 

[TSandM]

I don't know; GUE counts oxygen and nitrogen as narcotic.

 

[Mike Edmonston]

I don't know; GUE counts oxygen and nitrogen as narcotic.

So does NAUI.

 

[Rick Inman]

So does IANTD.

 

[FIXXERVI6]

What do most people around here use for an equivalent nitrogen depth at their deepest point when using trimix?

I understand that there are often standard mixes of trimix, but considering how expensive helium is, and if you can shave off some of the price by going with a lower He amount, then what will you tolerate for a maximum END?

I stick to standard mixes and keep the END 100 or less.

As for cost, if your going to start doing a lot of mix get a RB and/or build your own fill station.

BAUE Standard Mixes

 

[wedivebc]

So does IANTD.

Are you sure about that?

 

[Rick Inman]

Are you sure about that?

Well, I thought so. I just checked my notes and see where I wrote both EAD and END formulas. But It's possible that the instructor, not the book material, is the source of the END formula.

Later today I'll dig up the books and double check.

 

[Rick Murchison]

... It's possible that the instructor, not the book material, is the source of the END formula. ...

One thing's for sure... in researching who says what, I've found that there is a lot of misinformation floating around the internet about EAD and END - how they're calculated, what they mean, and how they're used.
Scary!:11:
My recommendation: Drop the term "Equivalent Nitrogen Depth" from your diving lexicon and follow the NOAA guidelines for figuring your END (Equivalent Narcotic Depth).

The formula is... END(in Atmospheres) = (1-He fraction)*ATA

Example: for Trimix 16/50 at 50M/165 FSW,

END = (1-.5)*6 = 3 Bar, 20M, 66FSW

From the NOAA Diving Manual
"16.3.1.2.4 Equivalent Narcotic Depth
... since oxygen has some narcotic properties, it is appropriate to include the oxygen in the END calculation when using trimixes (Lambersten et al. 1977,1978). The non-helium portion (i.e., the sum of the oxygen and the nitrogen) is to be regarded as having the same narcotic potency as an equivalent partial pressure of nitrogen in air, regardless of the proportions of oxygen and nitrogen. ..."

Rick