If you had to choose, 80% or 100% for deco gas and why.

[PfcAJ]

There's no peer reviewed anything for the csn clock. It's a made up thing.

Like i said, people have toxed below 100% and have FAR surpassed 100% without toxing. So what exactly is "100%" a measure of?

 

[danvolker]

That's what the HP149 of O2 is for, Dan. No need to carry the damn thing with you, though.

Since AJ and I (and any peer-reviewed scientific paper of which I'm aware) have different understandings of the word "demonstrably", I'll just let this drop. Though maybe I should ask if the DIR distaste for high ppO2 and END isn't also bogus, since it's "demonstrably" not a problem for plenty of us who dive deep air?

Doc....so are you saying that you would have 80/20 mixed and filled in some tanks....and then also bring a big tank of 100%? I suppose this does some of what I care about, though with an awful lot of bother.....where it does not work so well, is where someone needs to get out of the water, and needs to be on 100% as they go from ten feet down --- to the surface, and on to the boat....because they are already cascading badly with bubbles....and maybe no longer finding in-water to be the best place with ongoing complications.
The worst time for creating more massive growth of bubbles to block the vascular system, is going to be climbing out of the water, with all the exertion this creates....if they are already experiencing DCS, this is a really good time to be on pure O2 rather than 80/20.....This was one of George's points in his Bakers dozen, though I relay it in a nicer way, obviously

I have to say on the many times in the past couple of years that I have seen tech divers with 80/20 mix, I barely think about it....and would not consider broaching a discussion about it with them.... I just don't think this is a big deal. It is your religious conviction to use 80/20 and all that it comes with...it is mine to use pure O2 and what it comes with. And I really don't feel like doing religious discussions !!!

Someone asked about some of our opinions on this topic........ I guess it should have been obvious that all the jihadists on both sides would decide that they would need to step up...the whole-- "My god is better than your god thing".
I am more ready to make fun of this whole issue, than to argue it further.

 

[Dr. Lecter]

I am more ready to make fun of this whole issue, than to argue it further.

TITCR :d

---------- Post added July 16th, 2014 at 02:29 PM ----------

I'm going to tweak your statement a bit, but stay completely inside the logic you're using:

People have toxed below 1.6 and have FAR surpassed 1.6 without toxing. So what exactly is MOD a measure of?

HTFH...you should obviously be on your 100% at 30' (or deeper). It's more efficient!

 

[PfcAJ]

I think MOD is a pretty well defined item. The cns clock isn't though. "100%" doesn't really mean anything.

Im not sure what HTFH means.

You would be more efficient at 30ft. But the frequency of toxic events goes up quite a bit in test subjects. No thanks, 1.6max for me.

 

[daniel f aleman]

The real answer is that using either is perfectly fine. Nitpicking is a lot of fun though...

 

[TONY CHANEY]

I guess what I meant was that in the planning for any tech dive, part of the logistics is 100% O2 available on the boat. On the local boats that I dive, that means a 6 foot tall O2 tank, not a DAN recreational O2 kit. I guess if you were diving from a private boat, then it would be up to you to have that available, and that might well be in the form of extra bottles. But that's a separate thing from the gas that you are planning to use for your dive.

So whether your emergency O2 on the boat is a big tank or a few extra 40s of O2, I don't see how that requirement influences what you chose to bring with you on your dive (80 vs 100), which was the OPs question.

But I do appreciate the stylistic advice, Dan..! As someone new to the world of tech diving, I want to look good...

For all those reading this please do not forget that there is a great difference between a demand valve and passive valve. A demand valve requires that the diver / patient is able to breath on their own and a passive valve provides O2 even when the dive cannot breath on their own. So it really matters little if you have a tank full of O2. If the patient cannot inhale the O2 then it is of no use. And by the way, you cannot swap out the regs from a rescue tank to a scuba tank. I hope that this helps.

 

[kelemvor]

And by the way, you cannot swap out the regs from a rescue tank to a scuba tank. I hope that this helps.

Sure you can

 

[TONY CHANEY]

Sure you can

It is about time that somebody came up with a solution. I like it!

 

[nadwidny]

While I should know better than to ask for a rational discussion of this, I'm not going to let this ipse dixit just slide by without you backing it up. The fact that 100% works or that there is 20% N2 in 80 vs. 0% N2 in 100 isn't what I'm questioning - it's whether the relative efficiency has any significant difference. Having personally used both mixes on similar OC dives in the 200-300 range, I've never noticed any difference in how I felt afterwards. With 100 I took air breaks, had a higher CNS, and got out a few minutes sooner; with 80, fewer/no air breaks, lower CNS, got out a few minutes later.

The only chart in a textbook that I've ever seen shows surprisingly few differences among EAN mixes in terms of relative deco efficiency. So, where's your evidence 80% is significantly less effective than 100%?

If 80/20 was better than 100% they would be using it in chambers.

 

[lowviz]

It pains me to like your post, but I guess you guys would know...