PPO2 maximum safe value: 1.4, 1.6

[Storker]

I don’t really see what you’re getting at here.

It was an attempt to indicate - somewhat light-heartedly - that I didn't see much of a connection between the post you quoted and your answer. Kind of a non sequitur for me.

 

[Dan_P]

It was an attempt to indicate - somewhat light-heartedly - that I didn't see much of a connection between the post you quoted and your answer. Kind of a non sequitur for me.

I figured

My post was simply indicating that I agree with you to a large extent that keeping the ppO2 lower also handles gas density (in most cases, at least recreationally).
And that I care less about whether instructors teach gas density (or simply stick to lower ppO2’s - I assume that was your point) than I do about whether they stay within reasonable limits.

 

[electric_diver]

Hence the idea that 1.6 is OK for quiet deco but not for the working part of a dive..

There is an underlying assumption in this that is wrong in some dives. Deco may not be "quiet". If you have to deal with current and a fixed exit point you may find yourself working very hard on the deco.

 

[rjack321]

The idea of doing cold water, low visibility, potentially silty, lake dives at 130ft with no helium at all (narced N2 wise but also on high density gas with CO2 accumulation) along all compounded with a ppO2 of 1.6 or possibly above if the mix is off a little bit... This whole plan scares me.

Seems like you are stacking a whole lot of factors against you here for a tiny increase in NDL. There is nothing down there worth all these individually small but additively not so trivial risks.

 

[Jay]

So long as the planned gas density is within reasonable limits, especially when in a class setting, I don’t have a problem.
I personally prefer to educate students on the ‘why’ of things, and I personally prefer standard gases.
But that’s just personal preference.

When it comes to taking uninformed students to as deep as 7,7g/L, my opinion is that if there’s an accident in that setting, the instructor and agency should be legally culpable.
That’s all.

I don’t think that’s a radical position or a strong way to phrase it.

Just wanted to say thanks @Dan_P re gas density. I'm relatively new to SB, a Rec diver, and had never heard of this until you brought it up. Since then I've found a few threads and articles on it, and even though it's reasonably unlikely to affect me inside Rec limits it's nice to know about. Thanks!

 

[Dan_P]

Just wanted to say thanks @Dan_P re gas density. I'm relatively new to SB, a Rec diver, and had never heard of this until you brought it up. Since then I've found a few threads and articles on it, and even though it's reasonably unlikely to affect me inside Rec limits it's nice to know about. Thanks!

You're most welcome, and thanks!
Dr. Simon Mitchell and Gavin Anthony
If you're interested in reading more about it, I'd refer to Rebreathers and Scientific Diving Proceedings, page 66, "Respiratory Physiology of Rebreather Diving" by Simon Mitchell and Gavin Anthony.

 

[Steve_C]

A responsible shop dispensing banked nitrox should be producing an accurate mix. +-2% is an industry standard,

That makes it anywhere from 30 to 34 on a requested 32.

I always analyze tank when I pick it up and label tank. Tanks are mine and I am the only one using them but in an emergency and some one else needs a tank good to know. Sometimes dives are canceled so tanks not used for a while so also good for me since now a days I usually dive 32, but over the years I have had mixes from 28 to 34.