Equivalent nitrogen depth

[spacemanspiff1974]

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?

 

[Rick Inman]

My trimix training is IANTD, which allows up to 130' END. However, I prefer to stay above 100'. And the deeper I'm diving, the less I am apt to count pennies on the HE.

I use GUE standard mixes as much as possible, which keeps my head where I like it.

Using double 100's, 45% is 90 cubes. Cutting it to 35% saves 20 cubes, which is how much money? We mix our own, so it just a couple of dollars. My instructor once told me that if I can't afford a full HE mix, I shouldn't be tech diving.

However, with that said, I know of people who routinely dive at 150' end. Not me, though.

 

[rjack321]

110ft END is about the highest I go and that's on easier dives (e.g. wall goes to surface). For tough dives (penetration/wreck) I like it closer to 65-80ft. Helium is cheaper than coffins.

 

[texdiveguy]

My target is 100' END for my trimix diving.

 

[PerroneFord]

However, with that said, I know of people who routinely dive at 150' end.

Wow really? If I wanted to dive loopy, I would just save the cost of the mix class. I'll be taking my mix class in the fall or next spring, and honestly, I'm going to be shooting for END of 80ft or so. If you can't afford the dive, stay home. And I'm not really going to be needing mix very often so this shouldn't be too big a deal.

 

[Meng_Tze]

The commonly accepted limit is a partial pressure of 3.14 ata for nitrogen to become narcotic (effectively diving air to 30m/100ft).

I have had dives where I felt absolutely fine (whether I was is up for debate) and others where I was narced at less than PN2=2.5 ata

BTW EAD shows the loading for nitrogen only; and END is the expression of both nitrogen and oxygen. Both are a valid method for calculating narcotic equivalence, depending on views of O2 narcotic effects.

 

[Mike Edmonston]

I like to keep it at 100ft max, most of the time I will run it at 80 to 90. I enjoy remembering....

 

[ianr33]

Depends on the dive. Warm blue water, 130ish is fine. Cold and dark,no more than 100.

 

[wedivebc]

BTW EAD shows the loading for nitrogen only; and END is the expression of both nitrogen and oxygen. Both are a valid method for calculating narcotic equivalence, depending on views of O2 narcotic effects.

It depends which agency you were trained with.

 

[Rick Murchison]

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.
If you really want to shave nits, the narcotic effect of oxygen is probably a bit less than nitrogen, (even though it has about twice the lipid solubility, so you'd expect it to be twice as narcotic, its tissue titres tend to be lower than an inert gas would be as it's a metabolized gas that's also scavenged by hemoglobin - in rats the brain tissue titre's about a sixth what you'd expect were the gas inert, which should more than compensate for the increased narcosis expected by lipid solubility) and the narcotic effects of Helium + Oxygen may still be a bit less, maybe.... but it ain't enough to spit at, so prudence dictates "it is best not to assume reduced narcosis for the oxygen fraction of the mix" (Uncle Ricky's Rule).
Of course if you stick to HeliAir it's a moot point
I don't use the term "Equivalent Nitrogen Depth" because we already define that as "EAD" - "Equivalent Air Depth," making the term redundant and unnecessary, and confusing as well...
--
To the spirit of the question... I shoot for a max END of 4 Bar - 30M/100FSW, but will accept 5 Bar/40M/132FSW.
Rick