Maximum Operating Depth (M.O.D.) S.C.U.B.A. Diving On Air.

[wetb4igetinthewater]

I believe this is it.
Objective vs. Subjective Evaluation of Cognitive Performance During 0.4-MPa Dives Breathing Air or Nitrox - PubMed

Thanks! That may have been the basis of the article that I read. I'll have to dig around.

What was the search terms you used to find that link?

 

[boulderjohn]

Thanks! That may have been the basis of the article that I read. I'll have to dig around.

What was the search terms you used to find that link?

I searched ScubaBoard using nitrox and narcosis. I found a post with the link.

 

[Boston Breakwater]

Hey, it went off topic at posts #6 and 7, but he didn't apparently notice or care at that time!

Hey, @tursiops How are you? Firstly, I work. Secondly, I had at least 10 members on my 'Ignore." list. So, yeah, I didn't apparently notice, because they weren't visible.
I was initially taught maximum depth for "Air." 220 fsw (Just to stay on topic.) You seem good at smart unrelated comments. I dive primarily with air.
As, of today. All the members on my "Ignore." list have been cleared. I didn't want to read egotistic, and childish comments. That was wrong of me, and I apologize to all that were "Ignored."
Just thought I'd let you know, because, I cherish you as a valued member, and you have some of the most pertinent points on S.B.
My dedicated "Air." Bottles are Faber L.P. 121's (Using 3000 P.S.I. ) as a baseline, that's approximately 151 cubics per bottle.
I'm looking forward to your future comments....They're very helpful.

 

[tbone1004]

@Boston Breakwater check your math. 3000psi on lp121's is only around 137cf. Volume calculated at 2640psi not 2400psi. They're roughly 151cf at 3500psi due to nonlinear compression and what not

 

[Boston Breakwater]

@Boston Breakwater check your math. 3000psi on lp121's is only around 137cf. Volume calculated at 2640psi not 2400psi. They're roughly 151cf at 3500psi due to nonlinear compression and what not

Hello @tbone1004 You're right on time.....LOL. You were also on my "Ignore." list, but alas no longer. "Welcome Back." mainly for pedant responses, and you've immediately come through with one. (Your'e awesome.) I put an approximation in the post. "that's approximately 151 cubics per bottle. Thanks for being you.
Cheers.

 

[tursiops]

I was initially taught maximum depth for "Air." 220 fsw

So you were were taught to use PPO2MAX=1.6. Ok. Why was your OP asking about 1.4?

 

[Boston Breakwater]

So you were were taught to use PPO2MAX=1.6. Ok. Why was your OP asking about 1.4?

@halocline the argument for helium below 100ft that @PfcAJ has basically nothing to do with ppO2. @Boston Breakwater saying something off topic is not where that post went sideways.
We have 2.5 variables that weigh into MOD for any particular gas
First and foremost is ppO2 which is heavily emphasized in nitrox courses due to oxygen toxicity and is unfortunately the only variable that is really taught in most courses. That ppO2 limit is personal preference and can go anywhere from 1.0 to 2.0. 1.6 is the accept MOD that is used for marking bottles. In that case, Air has a MOD of 220ft.

Once we start getting into trimix classes, narcosis starts becoming very important, and when we start to talk about deep air it is obviously very important. A combined ppO2+ppN2 less than 4 is my personal preference. Research is saying that O2 is just as narcotic to us as N2 and where best mix for trimix used to only set N2 to some limit, I think it is much more prudent to set the combined partial pressure to 4. That happens to be 100ft, and that is the point where symptoms of hubris, dark narc, memory issues, and overall processing power/situational awareness become an issue. Again, you can set that limit to whatever you want, but the agencies normal recommendation is to set ppN2 to a max of 4.0, or set a combined ppO2+ppN2 to 4.0. In this case the MOD of air would be 132fsw or 99fws.

The half variable. I say half because it is really a subset of the narcosis variable, and that is gas density. Why does gas density matter? When you are trying to breathe, and it gets harder to breathe, you have a natural tendency to start breathing shallow which leads to CO2 retention in the lungs. CO2 is 20x as narcotic as nitrogen and can lead to all sorts of issues. CO2 is a scary effing gas and downright deadly. This is part of the reason that many divers consider DPV's a required piece of safety equipment when diving to trimix depths in order to limit the production of CO2 by minimizing exertion. It's the reason that many well known divers have died, most notably David Shaw, and I firmly believe is the real reason that most people get narc'd, not nitrogen. Unlike N2 though, it doesn't clear immediately after you get to a shallower depth, and it has lingering effects *my least favorite is a horrific headache at the base of your skull that lasts for over a day*. Based on that, the MOD for air is something that you have to choose for yourself. For me? It is variable. I'm much less reluctant to dive air to 180ft on a lazy drift dive in a bathing suit than I am to do a 180ft cave dive or even to go that deep in our local lakes which are cold and dark. I stand with AJ that below 100ft I want to have helium, though I don't consider it a hard and fast rule. With CCR now I have a lot more helium in a lot sooner than I would on OC and it's noticeably better.
@tursiops It was initially what I was taught. It does not mean....that I still embrace it. A safety margin "Pillow." if you will? can be pretty comfy, especially filled with Goose down.
Most scuba training organizations recommend that divers limit the partial pressure of oxygen for a dive to 1.4 ata. A diver may choose to lower or raise this number depending upon the type of diving and the purpose of the breathing gas.
Cheers.

@tursiops It was initially what I was taught. It does not mean....that I still embrace it. A safety margin "Pillow." if you will? can be pretty comfy, especially filled with Goose down.
Most scuba training organizations recommend that divers limit the partial pressure of oxygen for a dive to 1.4 ata. A diver may choose to lower or raise this number depending upon the type of diving and the purpose of the breathing gas.
Please, expand the quote above.
Cheers.

 

[tursiops]

Please, expand the quote above.

??

 

[tbone1004]

??

i'll get there tomorrow after work. I think he's asking why I gave a range of ppo2 vs a set value

 

[Boston Breakwater]

i'll get there tomorrow after work. I think he's asking why I gave a range of ppo2 vs a set value

LOL. No @tbone1004 your right on. I was just asking @tursiops to "Click to expand." your quote. You know at the bottom of the quote where it says "Click to expand."
Cheers.