Ccr Diver From Ohio Died In Ginnie Springs Today...

[Seya]

presume with just over 1 year on the o2ptima, that he wouldn't really be considered "new" or "still learning" the unit, right? I ask out of ignorance. I have read there is a very steep learning curve and seen several post about hundreds of hours being needed on a unit to get to know the HUD light signals for

It takes 5 seconds to learn the HUD green is good red is high yellow is low

 

[KenGordon]

So correct me if I'm wrong, it sounds like the diver completely bailed from the CCR as the report states "no reg in mouth" "attempts to put reg back in mouth and purge". Can you go back to the loop once it has been removed?

It sounds like one of two things was the cause of this accident.

1) The diver experienced a malfunction/failure of the unit.
2) The diver made an error while preparing the unit.

Does that sound right?

And for those of us that don't have first hand knowledge of CCR's (but are interested), hypothetically speaking and given what we know, is hypercapnia the most logical explanation for the cause of death?

I realize this is a very serious condition? Other than bailing out, what else can a diver do to survive? I know full face masks aren't very popular (expensive), but could using one, especially one that allows swapping regs, make a difference? For example, could you swap the loop for an OC reg and even if you pass out from co2 atleast you wouldn't drown.

If these are silly question, please forgive my ignorance about CCR's. While I have a little knowledge about how they operate I obviously don't know all there is to know.

I do not think you can say anything about the causes given the information available. The only facts are that he bailed out and he died. Did he need to bail out? Maybe, maybe not. We do not know and cannot tell why. Once a proper investigation looks at the unit perhaps it will be clear why he bailed out, but perhaps not.

Co2 issues are not just about the unit. How the user breaths, how much work they are doing, the gas being used and the depth are all factors.

If you come off the loop and shut it then you can go back on. If it is left open then the unit is likely to flood and become unusable.

 

[H2Ocaver]

I am not commenting on a particular cause of this event, but rather things that all RB divers should be aware of when discussing results that might appear like this incident. You kinda added a third there with Hypercapnea, but even very small amounts of CO can build up and cause the effect that was observed. Also, there are a myriad of health issues that can cause disorientation. When trying to quantify the number of POSSIBLE causes for accidents on rebreathers you end up with a list longer than the parts list of the RB. The you could add in any health issue that would be possible. A list of possible open circuit causes would only be slightly shorter.

James, you are just down the road from me and are welcome to stop by any time to take a look at a few RB's and ask any questions you want-Eric

So correct me if I'm wrong, it sounds like the diver completely bailed from the CCR as the report states "no reg in mouth" "attempts to put reg back in mouth and purge". Can you go back to the loop once it has been removed?

It sounds like one of two things was the cause of this accident.

1) The diver experienced a malfunction/failure of the unit.
2) The diver made an error while preparing the unit.

Does that sound right?

And for those of us that don't have first hand knowledge of CCR's (but are interested), hypothetically speaking and given what we know, is hypercapnia the most logical explanation for the cause of death?

I realize this is a very serious condition? Other than bailing out, what else can a diver do to survive? I know full face masks aren't very popular (expensive), but could using one, especially one that allows swapping regs, make a difference? For example, could you swap the loop for an OC reg and even if you pass out from co2 atleast you wouldn't drown.

If these are silly question, please forgive my ignorance about CCR's. While I have a little knowledge about how they operate I obviously don't know all there is to know.

 

[Jack Hammer]

It sounds like one of two things was the cause of this accident.

1) The diver experienced a malfunction/failure of the unit.
2) The diver made an error while preparing the unit.

Does that sound right?

It's really not that simple. It could be a medical issue, bad gas, something unknown and completely random, etc. A lot can go wrong in a cave and Murphy is always waiting, patiently.

 

[CuzzA]

Thanks for clarifying. And I definitely don't want to speculate on this incident, rather, given it's a possibility I was curious as to what the solutions are and I hope I was clear about generally hypothesizing in my earlier post.

Eric, I will stop by to chat sometime. It's good to see you on this board.

 

[DA Aquamaster]

So correct me if I'm wrong, it sounds like the diver completely bailed from the CCR as the report states "no reg in mouth" "attempts to put reg back in mouth and purge". Can you go back to the loop once it has been removed?

It sounds like one of two things was the cause of this accident.

1) The diver experienced a malfunction/failure of the unit.
2) The diver made an error while preparing the unit.

Does that sound right?

And for those of us that don't have first hand knowledge of CCR's (but are interested), hypothetically speaking and given what we know, is hypercapnia the most logical explanation for the cause of death?

I realize this is a very serious condition? Other than bailing out, what else can a diver do to survive? I know full face masks aren't very popular (expensive), but could using one, especially one that allows swapping regs, make a difference? For example, could you swap the loop for an OC reg and even if you pass out from co2 atleast you wouldn't drown.

If these are silly question, please forgive my ignorance about CCR's. While I have a little knowledge about how they operate I obviously don't know all there is to know.

Answers in no particular order:

Yes, the diver bailed out to OC and was on OC when the instructor came upon him. I don't think anyone has indicated when he bailed to OC or how long he was on OC before the instructor found him. Anything else is speculation.

WHY he bailed to OC is also speculation, but the preliminary inspection of the Rebreather by the recovery team did not disclose any faults with the rebreather. Generally speaking the advice is to bail out to OC if you "feel funny", and as Mel Clark states in her rebreather books, "if you feel funny you might be about to die". In short, you bail out if there is any doubt, get a couple sanity breaths and then diagnose if there is a problem.

Depending on the problem you encounter on CC, you can often solve the problem and go back on the loop, and that's the focus of technical rebreather training, or you can just stay on OC and end the dive on OC - which is the focus of recreational rebreather training.

Many problems are caused by user error in the assemble or pre-dive check procedures, such as the diver improperly packing a scrubber, or failing to properly perform positive and negative pressure checks, leading to a leak, but things also go wrong during the dive. There are indicators that can be observed and cross checks made while diving to detect problems, but it requires the diver to pay attention to the unit during the dive. For example sensors may fail or give incorrect readings (they may get wet, or be old and current limited, etc), electronic connections may fail, and valves and solenoids may fail closed (not supplying O2 to the loop) or fail open (supplying too much O2 to the loop). Those faults will usually be detected by the readings on the HUD and/or handset, through readings that are inconsistent, or don't make sense, particularly after flushing the loop with diluent.

The diver can also lose the DSV or BOV (a DSV with a built in bailout regulator) and flood the loop, but most units have decent water trapping ability and prompt action can limit it to a partial flood that can be cleared, and provided the scrubber is not affected, the loop can be de-watered and the diver can go back on the loop. In the extreme, the unit can completely flood and be very negative in the water.

Full face masks are a mixed bag. On the one hand it ensures the loop or OC bailout reg stays attached to the diver's airway, but in some circumstances that's a bad thing as it can increase the time and complexity of bailing out to OC.

A BOV offers similar pros and cons over a DSV (which just allows you to close the loop any time it is out of your mouth to prevent flooding the loop). On the one hand, bailing out is as simple as pulling a lever to close the loop and activate the OC reg, but on the other hand, unless you've got off board bailout, the rebreathers on-board bailout gas (the diluent) is very limited, so it's only a temporary solution before you'd have to bailout to off board gas, and if the reason for the bailout is caustic in the loop, it will also affect the OC bailout reg incorporated in the BOV.

Passing out from CO2 isn't your first response. Elevated CO2 levels will first cause a significant increase in respiration rate and once you get too far into that territory, the high CO2 and rapid breathing (which results in very inefficient exchange of O2 and CO2 in the lungs) will cause the diver to breath his bailout gas at alarming rates, several times higher than normal, and the condition may persist for the remainder of the dive (or the gas supply). My take away over the years is that divers who have had a CO2 hit on a rebreather, carry a lot more bailout gas than divers who have not and I've heard it said that you can identify CCR divers who have CO2 hit by the large amount of bailout gas they carry.

Fortunately, a CO2 hit is one of the more preventable failures, by paying close attention to scrubber packing and scrubber duration (which is reduced in cold water, and in higher workload conditions), not over breathing the loop in high workload conditions (the scrubber needs a certain minimum dwell time to scrub the gas) and by ensuring the mushroom valves that direct the flow through the loop are functioning and are in good condition.

It takes 5 seconds to learn the HUD green is good red is high yellow is low

That's very unit and or electronics specific.

For the purposes of CuzzA's post/questions, our HUDs for example display amber at a PO2 of 1.0, flash green once for every .1 over 1.0, and flash red once for every .1 under 1.0. So for example in air at the surface at a PO2 of .21, I'll see 8 red flashes - and that's actually still a breathable loop, but well below the minimum I'd recommend. At the other end at a PO2 of 1.8 I'll get eight green flashes and despite the green color, that'll kill me a lot faster than 8 red flashes.

The HUD itself just gives you a constant method of monitoring the loop in the 3-4 minute intervals between the times you should be looking at the hand set to read the sensors and other information displayed there.

 

[CuzzA]

@DA Aquamaster, thank you for the very detailed reply. Very informative.

Edit: I know CCR units closely monitor O2, but do CCR units also come standard with a CO2 monitor/alarm to avoid or alert you of going past the point of entering a dire situation?

 

[muzikbiz22]

@DA Aquamaster, thank you for the very detailed reply. Very informative.

Edit: I know CCR units closely monitor O2, but do CCR units also come standard with a CO2 monitor/alarm to avoid or alert you of going past the point of entering a dire situation?

Some units do, and the opinions out there are varied as to their value, and whether they work & are dependable. My particular unit has one, and works just perfectly. There is a great article on CO2 sensors in the current Alert Diver mag from DAN.

 

[kelemvor]

For the purposes of CuzzA's post/questions, our HUDs for example display amber at a PO2 of 1.0, flash green once for every .1 over 1.0, and flash red once for every .1 under 1.0. So for example in air at the surface at a PO2 of .21, I'll see 8 red flashes - and that's actually still a breathable loop, but well below the minimum I'd recommend. At the other end at a PO2 of 1.8 I'll get eight green flashes and despite the green color, that'll kill me a lot faster than 8 red flashes.

The HUD itself just gives you a constant method of monitoring the loop in the 3-4 minute intervals between the times you should be looking at the hand set to read the sensors and other information displayed there.

Thanks, now that you spell it out, I recall this being the basis of the description I was given on why it took a very long time to become proficient. I believe the instructor was talking about being intimately familiar enough to know what the various flashes meant without having to really "think about" it.

Was the instructor blowing the importance out of proportion?

Do you think the time Diver B had on his RB was sufficient to have this level of proficiency?

Does the shearwater NERD product eliminate the need to rely on the colored flash based HUD visual feadback system or does it simply augment that system or some other third thing?

 

[kelemvor]

Careful with the google as there are a few very out of date copies of that accident list that are being hosted. Better going to the source each time Deep Life Design Team: databases and analysis of rebreather accident data

Some more links of interest for those that want to educate themselves about how rebreathers work:
Deep Life Design Team: Design Submission for Open Revolution
Deep Life Design Team: Selected Design Validation Reports for Open Revolution Rebreathers
http://archive.rubicon-foundation.org/xmlui/bitstream/handle/123456789/9902/a550047.pdf?sequence=1
and more generally because it is an excellent source Rubicon Foundation
https://www.diversalertnetwork.org/files/Tech_Proceedings_Feb2010.pdf
Scuba Diving Medical Safety Advice — DAN | Divers Alert Network
https://www.diversalertnetwork.org/...UHMSProceedings/2014_UHMS_Proceedings_WEB.pdf
How Does Your Rebreather Scrubber Handle the Deep?
and more generally because of the depth of his expertise rebreathers John Clarke Online
http://dhmjournal.com/files/Fock-Rebreather_deaths.pdf
http://spums.org.au/sites/default/files/DHM Vol43 No2 compact.pdf
and for the novice perhaps best of all Richard Pyle's learners guide LGRB

Brad,

A lot of the links on that site are bad (404 error) or corrupt "This video cannot be played because the file is corrupt". If you have some contact with the "Deep Life Design Team" company, could you mention it to them? It seems there may be some interesting information there despite the conflict of interest concern mentioned by Ken Gordon. The details may help laymen such as myself better understand what's involved in rebreather accidents, so I think it's relevant to the thread at least.