Cave Ccr Student Dies At Blue Grotto Today

[cool_hardware52]

how will you know you aren't moving in the water column. Is this a case when you can't see your HUD or your computer but can your depth? If the argument is you can "feel it" I have pretty good buoyancy and in a zero viz silt I won't be wanting to trust my life on "feeling" my depth. Sorry

My ears will tell me if I've changed depth by more than 1/4-1/2 ATA. Is 1/2 ata typically going to make the gas in the loop dangerous to breath for a minute? Maybe if you were quite shallow and the loop was near hypoxic to start with, but other than that I don't see how.

Tobin

 

[scuba5150]

Why do you think you're entitled to know everything about an accident within just a few hours of it happening? Do you lack the decency to think that the families of those involved should have some time to be informed, get over the shock, and begin to grieve?

Several of us just watched a train wreck of speculation on FB because a small group of people made gross determinations without having anything more substantial than hearsay and rumor.

Chill people.

The Law Offices of David G. Concannon, LLC

Reading your link reinforces why I newer wanted to go to law school. Just sayin"

 

[The Chairman]

Reading your link reinforces why I newer wanted to go to law school. Just sayin"

The problem is that we are at cross purposes with the lawyers. They want to control and obfuscate the facts to strengthen their case. In contrast, we want to figure out what went wrong so we can prevent further loss of life. They are worried about money and we are worried about survival.

As for the blame fest that happened on Face Book, that would be hard to do here. I'm pretty proud of that fact.

I'm really frustrated and tired of how slow facts are revealed about diving incidents. It's in the public interest to identify these risks and dive in a manner that reduces them. These guys are like a bad Jack Nicholson imitation: "You want the truth? You can't handle the truth!" Yeah. Let us be the judge of that.

 

[cerich]

My ears will tell me if I've changed depth by more than 1/4-1/2 ATA. Is 1/2 ata typically going to make the gas in the loop dangerous to breath for a minute? Maybe if you were quite shallow and the loop was near hypoxic to start with, but other than that I don't see how.

Tobin

In zero viz I can still read my HUD and computer since colour OLED units came out. Sorry, not gonna trust my ears, you are welcome to trust yours.
I only have ~6000 dives, when I get more experience I may change my thoughts on that

 

[DA Aquamaster]

Simulating zero viz is one thing and with ccr huds/monitors you would still be able to see your information even in silt so thick you can feel it. Using those blackout masks is almost like simulating a CCR head hardware/software failure in a sense - you can no longer see your information. Two different things. At that point the CCR is a $12,000 paper weight and it's time to abandon ship and bailout.

Exactly. For example, we went through Harry's crack from the mud tunnel side on our recent N FL trip and the last bit going in that direction can result in zero viz, particularly when you put in the jump back to the gold line. Even in those low viz conditions, I could still see the HUD, and Marci, coming behind me, in near zero viz after I put in the jump, who actually confirmed the jump line by put putting her mask up to it to confirm it was our neon green jump line rather than the white line of a T, could still see her HUD as well.

Every time I have called a training dive, my instructor has praised my decision. That's true for both cave and CCR. I have heard instructors berate students for NOT calling a dive. It's a part of the learning curve, or at least it should be.

We'd had a similar experience on a class dive and the short story is that calling the dive was an expected event, and not calling the dive would have been a "fail". If a diver hasn't got the balls and the sound judgement to say enough is enough and turn the dive when the prudent parameters for calling the dive are reached, and instead thinks he or she is going to just rely on the instructor to safely complete the dive, that diver has no business cave diving.

how will you know you aren't moving in the water column. Is this a case when you can't see your HUD or your computer but can your depth? If the argument is you can "feel it" I have pretty good buoyancy and in a zero viz silt I won't be wanting to trust my life on "feeling" my depth. Sorry

I spent a number of years doing inland commercial diving in zero viz, and if you pay attention, you'll note both the chance in buoyancy (and suit volume if you've got a dry suit) and in most cases the changes in pressure on your ears as the depth changes even in zero viz. That's even easier in a cave diving situation where you're also maintaining neutral buoyancy. On a rebreather, any significant change in depth over a reasonable short period of time will also change the volume and buoyancy of gas in the loop - much faster or slower than you'd expect from metabolizing the O2 in the loop. In a cave, you may also have the advantage of knowing the profile of the cave in that section and knowing the line you are following is fairly level. You have some resources you can use in an emergency, you just need to be aware of them and pay attention.

-----

In any case, if you're running the loop at minimum loop volume, you've have an electronics failure and the depth is constant, then you can be reasonably confident that any change in loop volume is due to metabolizing O2. Consequently if you had a safe PPO2 well within the acceptable, life supporting PPO2 range when the electronics quit, and the depth remains constant, then you have the option of staying on the loop by adding as needed just enough O2 to maintain minimum loop volume since you'll be maintaining a safe PPO2 by adding back in only enough O2 to replace what you metabolized.

But if you have any doubt of those facts, or the depth changes, or you question the accuracy of the PPO2 reading before the electronics took a dump, you need to go to another option.

Another option might be doing a dil flush to establish a known to be good volume of gas in the loop at the PPO2 for that depth with your diluent gas. Then run it in SCR mode, paying due regard to depth to ensure you're cycling the gas out of the loop and adding more diluent frequently enough to maintain an adequately high PPO2 - which becomes increasingly critical as you get shallower, and is even more critical with deeper diluent mixes with lower O2 content. Part of that strategy will be doing a dil flush after every significant decrease in depth as you exit the cave, to ensure you have a high enough PPO2.

Once you get to 20' you can do a thorough O2 flush and then run the unit as an O2 rebreather, maintaining minimum loop volume to ensure the PPO2 stays in the 1.2-1.4 range during your deco.

And of course at any point you have the option of bailing out to OC, but the focus in most technical CCR courses is to develop the ability to stay on the loop if it is both possible and prudent to do so in order to increase your options and preserve maximum amounts of bailout gas in case things continue to go down hill and you end up with a catastrophic loop failure.

 

[cerich]

Exactly. For example, we went through Harry's crack from the mud tunnel side on our recent N FL trip and the last bit going in that direction can result in zero viz, particularly when you put in the jump back to the gold line. Even in those low viz conditions, I could still see the HUD, and Marci, coming behind me, in near zero viz after I put in the jump, who actually confirmed the jump line by put putting her mask up to it to confirm it was our neon green jump line rather than the white line of a T, could still see her HUD as well.



We'd had a similar experience on a class dive and the short story is that calling the dive was an expected event, and not calling the dive would have been a "fail". If a diver hasn't got the balls and the sound judgement to say enough is enough and turn the dive when the prudent parameters for calling the dive are reached, and instead thinks he or she is going to just rely on the instructor to safely complete the dive, that diver has no business cave diving.



I spent a number of years doing inland commercial diving in zero viz, and if you pay attention, you'll note both the chance in buoyancy (and suit volume if you've got a dry suit) and in most cases the changes in pressure on your ears as the depth changes even in zero viz. That's even easier in a cave diving situation where you're also maintaining neutral buoyancy. On a rebreather, any significant change in depth over a reasonable short period of time will also change the volume and buoyancy of gas in the loop - much faster or slower than you'd expect from metabolizing the O2 in the loop. In a cave, you may also have the advantage of knowing the profile of the cave in that section and knowing the line you are following is fairly level. You have some resources you can use in an emergency, you just need to be aware of them and pay attention.

-----

In any case, if you're running the loop at minimum loop volume, you've have an electronics failure and the depth is constant, then you can be reasonably confident that any change in loop volume is due to metabolizing O2. Consequently if you had a safe PPO2 well within the acceptable, life supporting PPO2 range when the electronics quit, and the depth remains constant, then you have the option of staying on the loop by adding as needed just enough O2 to maintain minimum loop volume since you'll be maintaining a safe PPO2 by adding back in only enough O2 to replace what you metabolized.

But if you have any doubt of those facts, or the depth changes, or you question the accuracy of the PPO2 reading before the electronics took a dump, you need to go to another option.

Another option might be doing a dil flush to establish a known to be good volume of gas in the loop at the PPO2 for that depth with your diluent gas. Then run it in SCR mode, paying due regard to depth to ensure you're cycling the gas out of the loop and adding more diluent frequently enough to maintain an adequately high PPO2 - which becomes increasingly critical as you get shallower, and is even more critical with deeper diluent mixes with lower O2 content. Part of that strategy will be doing a dil flush after every significant decrease in depth as you exit the cave, to ensure you have a high enough PPO2.

Once you get to 20' you can do a thorough O2 flush and then run the unit as an O2 rebreather, maintaining minimum loop volume to ensure the PPO2 stays in the 1.2-1.4 range during your deco.

And of course at any point you have the option of bailing out to OC, but the focus in most technical CCR courses is to develop the ability to stay on the loop if it is both possible and prudent to do so in order to increase your options and preserve maximum amounts of bailout gas in case things continue to go down hill and you end up with a catastrophic loop failure.

If I don't KNOW my PPO2 I am bailing out. YMMV

 

[cool_hardware52]

In zero viz I can still read my HUD and computer since colour OLED units came out. Sorry, not gonna trust my ears, you are welcome to trust yours.
I only have ~6000 dives, when I get more experience I may change my thoughts on that

If you close your eyes do you start to lose your buoyancy immediately?

Keep in mind that Garth did qualify his statement with a time period of 1 minute.

But really, you can't tell you are rising in the water column with your eyes closed? It isn't going to keep me + or - a foot, but after ~1/2 ata all sorts of things become noticeable Ears, drysuit, etc.

Tobin

 

[DA Aquamaster]

If I don't KNOW my PPO2 I am bailing out. YMMV

So am I - if I'm in doubt at all about the PPO2, I'm bailing out right now, particularly if I'm worried about a very low PPO2.

But think about it for minute and consider how else you can "know" your PPO2. Sensors are not needed to get a breathable loop in the short term while you start to diagnose what's going on. Bailing out is always an option, but it's not the only option if you've got a proper diluent mix.

You can do a dil flush to get a breathable loop for a minute or so, as the diluent mix combined with your depth is a reliable means to know your PPO2 in the event of an electronics failure and/or sensor readings that don't make sense or are suspect. And it's also a means to both push some dry gas past the sensors if they may be wet, and more importantly, to get a known mix in the loop to verify the sensor readings to see which sensors may be giving you valid information.

Now...applying that to a just occurred electronics failure where everything goes dark. If you had a breathable loop at minimum loop volume, your depth is constant and you don't have uncontrolled gas being injected into the loop, you've still got the option to run it at minimum loop volume to maintain the PPO2, at least until your depth changes.

If you're in doubt about the PPO2 when things got dark (which you shouldn't be if you were paying attention to the loop - unless perhaps the sensor readings were questionable before, or you've had a boom failure) you can still do a diluent flush and then run it as an SCR. Baling out is still an option but it's one of three, not the only one.

There are some circumstances where you need to bail out and need to do it right now. However, if a diver's response to each and every CCR issue is to just bail out, and then stay off the loop, then that diver probably shouldn't be doing technical CCR diving as he or she will need to have a better grasp of what's going on and have more tools in the tool box to deal with problems in an over head environment.

 

[CCRMichael]

That is directly contradicted by the TDI course standards linked to above.

No it's not. I was one of the people who wrote TDIs Rebreather cave standards. Read them more carefully. You need to be able to monitor PO2 at all times or the drill needs to be done on OC (bailout) seeing your HUD is monitoring your PO2. Every CCR Cave instructor I know including myself has the student stick their HUD inbetween the neoprene cover and their mask. All they can see is their HUD.

The neoprene mask covers make this drill safer. The student can see their PO2. If they have any problem they simply pull the mask cover off and they can see (their light is already on and they already have a mask on)

It's also way easier on the instructor as he can keep his lights on and easily monitor the student.

Just put the HUD in the cover. I have a taught students using 2 versions of Shearwater HUDs, AP huds, HH HUDs, Sentinel HUDs, Narkedat90 HUDs, AV1 HUDs etc and all could easily monitor their PO2 with their neoprene mask cover on.

 

[rongoodman]

Thanks for the explanation. Putting the HUD under the cover hadn't occurred to me.