Ginnie Springs diver missing - Florida

[rjack321]

for my education, why would you shut off oxygen and breathe it down. I was taught if it s a little high breathe it down. But if it’s that high I was always taught dil addition or dil flush. I personally wouldn’t want an in-line shut off on my oxygen. I believe when I did the sidewinder course there was a shutoff on the oxygen and I wasn’t a fan. But ai don’t remember Edd teaching me to shut off the oxygen and breathe it down. And definitely wasn’t taught to in the fathom course. So what would the benefit of breathing it down be other than avoiding having to dil flush or avoiding wasting oxygen.

When you have 32% BO/dil and are at 100ft you have to do a nearly complete dil flush to get the ppO2 to drop. If you're diving 50s and have to do it a few times a dive that's a significant cut into that gas. Sliding it off and breathing it down over 5mins seems so straightforward, and it is - until it's not.

 

[CptTightPants21]

When you have 32% BO/dil and are at 100ft you have to do a nearly complete dil flush to get the ppO2 to drop. If you're diving 50s and have to do it a few times a dive that's a significant cut into that gas. Sliding it off and breathing it down over 5mins seems so straightforward, and it is - until it's not.

I am shocked that turning off O2 for a nonemergency event is a taught procedure, especially on a mccr. This concept is completely alien to me. If I were to go CCR and was taught that I don't think I could do it.

Regarding 32%, that is more of a poor BO/dil choice. Not wrong, but inefficient given other readily available options

 

[rddvet]

If you don't shut off the O2 it can take 20+mins to breathe it down from 1.6 back to 1.1 depending on depth.

If you believe in hot dil and are at depth, then you may have an issue. When I'm in Ginnie/LR/JB/etc on EAN32 my ppO2 actually goes up when I dil flush since I run 1.1 but the dil ppO2 is 1.2-1.3.

When you have 32% BO/dil and are at 100ft you have to do a nearly complete dil flush to get the ppO2 to drop. If you're diving 50s and have to do it a few times a dive that's a significant cut into that gas. Sliding it off and breathing it down over 5mins seems so straightforward, and it is - until it's not.

It all makes sense. Personally if I was in Ginnie and hit a 1.6 that wasn’t just a quick spike, then I’d probably do the dil flush and accept only going down to 1.4 and that I wasted gas. But that is probably just due to my training. Breathing down a 1.4-1.5 is something we were taught. But I’m thinking if I’m above a 1.6 it’s because I’ve done something stupid so I’d fall back to dil flush. We were taught in that case bail out, figure out why it happened, dil flush. At this stage I don’t think I’d bail out.

 

[tbone1004]

I am shocked that turning off O2 for a nonemergency event is a taught procedure, especially on a mccr. This concept is completely alien to me. If I were to go CCR and was taught that I don't think I could do it.

Regarding 32%, that is more of a poor BO/dil choice. Not wrong, but inefficient given other readily available options

depends on what you are optimizing efficiency for. I strongly believe in diving an fO2 similar or exactly what you'd be doing on OC. It's way more efficient for cave diving than lean dils in terms of O2 consumption, but not for leaning out a high ppO2. The point though is they are breathable though, so accept the high ppO2 when you dil flush, and knock it down over time.

 

[rjack321]

Regarding 32%, that is more of a poor BO/dil choice. Not wrong, but inefficient given other readily available options

Not sure what you think is a good dil in this case. Do you dive a sidewinder or another SM CCR?

But in a cave if you bail and have to swim out on your BO/dil for an hour+ bringing air (or something with radically lower fO2) will rack up an insane amount of deco. The benefit of dil similar to your BO is that you end up with the closest match deco wise regardless if you are on the loop or bailed. Bringing 32% BO and separate air dil requires more cylinders, which makes for a larger profile, more drag, less able to fit in SM cave etc etc.

 

[CptTightPants21]

Not sure what you think is a good dil in this case. Do you dive a sidewinder or another SM CCR?

But in a cave if you bail and have to swim out on your BO/dil for an hour+ bringing air (or something with radically lower fO2) will rack up an insane amount of deco. The benefit of dil similar to your BO is that you end up with the closest match deco wise regardless if you are on the loop or bailed. Bringing 32% BO and separate air dil requires more cylinders, which makes for a larger profile, more drag, less able to fit in SM cave etc etc.

I think 21/35 or something close to that would be a better choice in this scenario. The mCCR with leaky valve vs a eCCR dynamic can also play a role in dil choice. You said it yourself--32% would take a lot to flush the loop and get it down. With an eCCR, 32% is a little more forgiving as you can flush it once and then no excess O2 will be added. If you have a leaky valve that is adding more O2 than your consumption rate and causing the O2 to gradually increase, the flushes will be less effective in fixing the issue and you would want a fO2 that is lower so that more time passes between flushes.

While I think that a HUD would probably have saved his life, I can't say that with 100% certainty. The lack of awareness for the amount of time it would take him to breathe down the loop and not look at your handset could be applied to a HUD as well. I think agencies making it a standards violation to turn off O2 for anything less than an emergency will save more lives in the long run.

 

[rjack321]

I think 21/35 or something close to that would be a better choice in this scenario. The mCCR with leaky valve vs a eCCR dynamic can also play a role in dil choice. You said it yourself--32% would take a lot to flush the loop and get it down. With an eCCR, 32% is a little more forgiving as you can flush it once and then no excess O2 will be added. If you have a leaky valve that is adding more O2 than your consumption rate and causing the O2 to gradually increase, the flushes will be less effective in fixing the issue and you would want a fO2 that is lower so that more time passes between flushes.

What dil are you diving to the henkel, or in mainland, or to the champagne bottle in hole in the wall, or to the stratosphere in JB now?

(nevermind the current fatality was more than double all of these penetrations and in a couple cases almost triple these distances on 3 years of CCR diving)

 

[_Slacker_]

The part of the cave mentioned is at trimix depths.

 

[rjack321]

The part of the cave mentioned is at trimix depths.

In this case yes, was trying not to get into having 18/45 as a dil but being somewhere other than at max depth. That is just all the more reason not to shut off o2 and breath it down though

 

[jale]

Hi
The "trick" of turning your oxy off (valve or inline) in a mccr can only be used if the ADV is also off. Indeed, the lost of buoyancy would act as a reminder you need to check your monitor.