How great is the risk (in your perception)?
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KevinNM
Contributor
Well, yeah. What “will be enough” when things go wrong is what is fuzzy.
I’ve read occasional posting by rebreather divers who went through what seemed like an outrageous amount of gas getting out after things went seriously sideways far enough back. It’s clear that the two guys in EN didn’t have enough gas to get out after things went sideways, but highly experienced EN rebreather divers have also said that they felt the amount of bailout the two unfortunate divers had was a reasonable amount.
Are you sure the student was in a position to know?
I ask as on my most recent course I basically said 'come on, nobody is really carrying enough for a full 45l/minute ascent, look you've only got an X and a Y...' which led to time spent on bailout planning vs deco planning. I was wrong, he had enough.
Having said that, I see people claiming bottom times that I cannot see done with the gas they carry. Some of those people also talk down team bailout. So they will be taking extra risk. However these are also the dives that are highly impractical on OC.
My view is that CCR can be riskier if you let it.
PfcAJ
Contributor
A ccr failure forced a bailout situation on one of the dives. The diver didn't have enough gas to complete the ascent and ended up sharing with a buddy.
Team bailout is nonsense.
lermontov
Contributor
I have only read part of the thread. So i apologise if this point has been made.
There are a lot of people commenting with no experience of CCR, and limited experience of technical OC diving. The risk of this is mis information and the generation of mis information.
Against this, is the vested interest of those that dive CCR.
1. OC is passive.
From a purely recreational point of view. OC is passive.
The gas is in the cylinder, you know everything is good because when you take a breath, you get gas. If anything is wrong you don't - you know you have a problem. Hopefully, your reactions and your buddies are such that you make a safe ascent to the surface.
Nitrox complicated the issues ( a little ). You need to know whats in the cylinder, and ensure that you don't over dive the gas. If you get this wrong then you either get DCI - leaner mix than that planned/dived; potential OxTox with all the risks of a fatality.
ADC / ERD(Accelerated Decompression Diving). Here you add the risk of breathing the wrong gas at the wrong time - OxTox again. Messing a gas switch (if you can't switch regulators you shouldn't be doing any diving, let alone this type). Missing a gas switch - DCI. Equipment Failure on a gas switch, this raises the issues of insufficient gas to complete the deco.
Trimix. Basically all off the ADC/ERD stuff. Plus issues with hypoxic mixes, breathing travel boxes to deep.
2. CCR is active
As has been pointed out previously. CCR's are active, they monitor the depth and mix, and remix on the fly.
It is also important to understand that there are two types of CCR, mCCR and eCCR.
As a general rule, mCCR monitor PO2 ONLY. They do not correct errors in PO2, or ALARM in the event of an issue.
They rely 100% on the brain of the diver. The diver corrects PO2 errors, identifies potential failures both equipment and PO2. For some, this is the strength, the diver doesn't get sloppy because he knows that he needs to continuously monitor the unit - or he/she is in trouble.
eCCR come in two flavours, all the bells and whistles, or minimal.
The minimal, controls the PO2, monitor obvious errors, cell issues, high/low PO2, and thats about it. Often this information is only available on the display.
The Bells and Whistles failures have auto PO2 switching, depth alarms, decompression computers built in, HUD's etc.
The mCCR group says that you can become too reliant on the electronics, and don't check the unit enough.(I have sympathy with this point of view - and I dive an eCCR).
The issues with CCR have been well discussed
CO2 breakthrough, - over diving the scrubber/wrong scrubber or degraded material/poor packing/poor assembly.
Cell Failure - resulting in high/low PO2's/ incorrect decompression etc.
Poor Cell calibration - as above.
Flooding - damage during the dive / poor assembly and predate checks.
The significant difference with CCR as a general rule is that you have TIME to analyse, and resolve a solution to your problem. With the exception of two issues, CO2 breakthrough (Which I believe is the biggest fear for most CCR divers). High PO2. With the exception of these two issues you can normally look at what is going on and plan a response.
I do agree that the mentality of the individual is important. CCR's need to be looked after. Maintenance, especially preventative. Assembly needs to be meticulous, hence the reliance on lists.
I do remember a summer where my OC kit was chucked in the back of the car, wet and salty. Probably would stay in the car all week, whilst I was away for work. Back to the coast at the weekend and straight back in the sea, back in the car at the weekend - etc. A quick buddy check and I know everything was working.
With a CCR I couldn't have done this, the cells would have been damaged, god only knows what would have grown in the counter lungs. I couldn't have trusted that things where working properly.
Gareth
PS - on team bailout. I have done this for real, when I was on OC. A buddies first stage failed at the stop. He went on to back gas. I finished my deco', then we swapped cylinders and he used my deco gas. The rest of the team handed me off their deco gas at the end of their dives, I went back on to deco gas for the rest of my buddies deco.
There are a lot of people commenting with no experience of CCR, and limited experience of technical OC diving. The risk of this is mis information and the generation of mis information.
Against this, is the vested interest of those that dive CCR.
1. OC is passive.
From a purely recreational point of view. OC is passive.
The gas is in the cylinder, you know everything is good because when you take a breath, you get gas. If anything is wrong you don't - you know you have a problem. Hopefully, your reactions and your buddies are such that you make a safe ascent to the surface.
Nitrox complicated the issues ( a little ). You need to know whats in the cylinder, and ensure that you don't over dive the gas. If you get this wrong then you either get DCI - leaner mix than that planned/dived; potential OxTox with all the risks of a fatality.
ADC / ERD(Accelerated Decompression Diving). Here you add the risk of breathing the wrong gas at the wrong time - OxTox again. Messing a gas switch (if you can't switch regulators you shouldn't be doing any diving, let alone this type). Missing a gas switch - DCI. Equipment Failure on a gas switch, this raises the issues of insufficient gas to complete the deco.
Trimix. Basically all off the ADC/ERD stuff. Plus issues with hypoxic mixes, breathing travel boxes to deep.
2. CCR is active
As has been pointed out previously. CCR's are active, they monitor the depth and mix, and remix on the fly.
It is also important to understand that there are two types of CCR, mCCR and eCCR.
As a general rule, mCCR monitor PO2 ONLY. They do not correct errors in PO2, or ALARM in the event of an issue.
They rely 100% on the brain of the diver. The diver corrects PO2 errors, identifies potential failures both equipment and PO2. For some, this is the strength, the diver doesn't get sloppy because he knows that he needs to continuously monitor the unit - or he/she is in trouble.
eCCR come in two flavours, all the bells and whistles, or minimal.
The minimal, controls the PO2, monitor obvious errors, cell issues, high/low PO2, and thats about it. Often this information is only available on the display.
The Bells and Whistles failures have auto PO2 switching, depth alarms, decompression computers built in, HUD's etc.
The mCCR group says that you can become too reliant on the electronics, and don't check the unit enough.(I have sympathy with this point of view - and I dive an eCCR).
The issues with CCR have been well discussed
CO2 breakthrough, - over diving the scrubber/wrong scrubber or degraded material/poor packing/poor assembly.
Cell Failure - resulting in high/low PO2's/ incorrect decompression etc.
Poor Cell calibration - as above.
Flooding - damage during the dive / poor assembly and predate checks.
The significant difference with CCR as a general rule is that you have TIME to analyse, and resolve a solution to your problem. With the exception of two issues, CO2 breakthrough (Which I believe is the biggest fear for most CCR divers). High PO2. With the exception of these two issues you can normally look at what is going on and plan a response.
I do agree that the mentality of the individual is important. CCR's need to be looked after. Maintenance, especially preventative. Assembly needs to be meticulous, hence the reliance on lists.
I do remember a summer where my OC kit was chucked in the back of the car, wet and salty. Probably would stay in the car all week, whilst I was away for work. Back to the coast at the weekend and straight back in the sea, back in the car at the weekend - etc. A quick buddy check and I know everything was working.
With a CCR I couldn't have done this, the cells would have been damaged, god only knows what would have grown in the counter lungs. I couldn't have trusted that things where working properly.
Gareth
PS - on team bailout. I have done this for real, when I was on OC. A buddies first stage failed at the stop. He went on to back gas. I finished my deco', then we swapped cylinders and he used my deco gas. The rest of the team handed me off their deco gas at the end of their dives, I went back on to deco gas for the rest of my buddies deco.
PfcAJ
Contributor
A single failure means you are no longer an independent diver and you are totally reliant on your buddy to ensure you don't drown or get bent. No where in technical diving is this appropriate. From day one dive planning is all about being able to independently survive at least one equipment failure without assistance. To me this is even more important in rebreather diving as the system is simply more complex. More seals, scrubber, one way valves, maybe electronics, and so forth.
The idea of "I can't carry enough gas to complete the dive" is just a symptom of a bigger problem: poor equipment configuration, lack of physical ability (either skills or fitness to do the dive), or lack of discipline (lazy, not managing bottom times, reluctance to buy the required gear, diving off a boat that's not equipped to accommodate the planes dive, etc).
Team bailout is bad practice.
The Chairman
Chairman of the Board
Dan_P
Contributor
I think this is an extremely interesting thread.
One thing that haunts me is, what if JYC decided O/C was silly and went with a CCR solution back in the day - would we all be diving CCR and O/C would be the "risky", "dangerous" voodoo-stuff?
On another note, my idea of how I wish to pursue CCR diving, and why:
One: I subscribe to a train of thought that O/C, which we - I assume - all started out learning and have developed with, is the base of the CCR. That is, conceptually, the breather function is simply a "plug-in" or "add-on" to what we've always used.
This means there's a correlation between diving O/C and bailing out. It also means I can recycle a lot of skills from day 1 to day 10.000.
Two: I believe that I can't rely on my CCR function to work and keep working, and don't want to bet my life on it doing so. I interpret this to have a direct implication to my gas logistics - i.e., I feel I must always have enough gas to finish the dive in O/C.
Three: If I can simplify the bailout process, so my logic goes, that will add safety in an OOG scenario. I.e., if I have several tanks hanging next to me, some of which will save my life and some of which will kill me, I would prefer not to have to fiddle around with what is effectively a gas switch procedure from a basis of being out of gas, as that would create a natural sense of urgency - thereby increasing the risk of picking the wrong bottle.
I'd prefer to use the same configuration for all my diving, certainly including dives where I have different gases next to me.
This means that to me, with this train of thought propelling my choice, a BOV makes quite a lot of sense.
Already at this point, my choices of approaches to the CCR question - to me, a gas logistics problem - have been limited greatly. Still a few ways around it, though, so carrying on:
Four: I don't feel that I can confidently say a single-user human-machine interface on an automated system, is a warranted solution to ensure safety for it's own sake.
That is, just because a system is automatic, doesn't mean it's safe. Even if the weak spot is the human operator, the system interaction may in fact be causal to a disasterous outcome. Look at overriden autopilots and "human error" (a term of diminishing value).
And I certainly am not willing to accept automation to achieve a sense of ease of operation (my logic is that I will want to confirm every action toward the desired outcome anyway).
Does this mean that an automated system (in the case of CCR solenoid, leaky valve or ADV) is inherently "bad" in my view? Absolutely not! It just means that I don't accept them off the bat.
On the contrary, my thinking leads me to the thought that they may well be very reasonable candidates for back-up systems. But as for the primary operation?
Five: I don't need an automatic boyancy valve to constantly adjust the volume in my BC. I don't need a leaky valve into my drysuit. Obvious to most, if I can't manage those systems, I should be doing "smaller dives" until confident.
If I'm running a breather fully manual (which is the backup to most electronic solutions anyway), I haven't my hands full. And if I do have my hands full, I can't dive anyway (BC/drysuit adjustments).
So the logic, for me, is do I want an automated system to be my primary and a manual to be my secondary, or the other way around?
For me, manually running an O/C platform with a CCR "plugin" while maintaining gas reserve to finish the dive on an integrated O/C, makes sense.
I think that, at least in terms of human/machine interface errors, a lot of risk is managed and diminished substantially, and the "hassle" is minimal.
The only thing is, a "solenoid can work deeper than a MAV". I don't know that I'll need to pull an aweful lot of 200m+ dives anyway, but if I do - do I really want to operate with no backup I expect to work, or a backup that I expect to work, but don't really love?
Such is my thinking as it relates to the OP question about perceived risks and my personal views on how to meet them.
One thing that haunts me is, what if JYC decided O/C was silly and went with a CCR solution back in the day - would we all be diving CCR and O/C would be the "risky", "dangerous" voodoo-stuff?
On another note, my idea of how I wish to pursue CCR diving, and why:
One: I subscribe to a train of thought that O/C, which we - I assume - all started out learning and have developed with, is the base of the CCR. That is, conceptually, the breather function is simply a "plug-in" or "add-on" to what we've always used.
This means there's a correlation between diving O/C and bailing out. It also means I can recycle a lot of skills from day 1 to day 10.000.
Two: I believe that I can't rely on my CCR function to work and keep working, and don't want to bet my life on it doing so. I interpret this to have a direct implication to my gas logistics - i.e., I feel I must always have enough gas to finish the dive in O/C.
Three: If I can simplify the bailout process, so my logic goes, that will add safety in an OOG scenario. I.e., if I have several tanks hanging next to me, some of which will save my life and some of which will kill me, I would prefer not to have to fiddle around with what is effectively a gas switch procedure from a basis of being out of gas, as that would create a natural sense of urgency - thereby increasing the risk of picking the wrong bottle.
I'd prefer to use the same configuration for all my diving, certainly including dives where I have different gases next to me.
This means that to me, with this train of thought propelling my choice, a BOV makes quite a lot of sense.
Already at this point, my choices of approaches to the CCR question - to me, a gas logistics problem - have been limited greatly. Still a few ways around it, though, so carrying on:
Four: I don't feel that I can confidently say a single-user human-machine interface on an automated system, is a warranted solution to ensure safety for it's own sake.
That is, just because a system is automatic, doesn't mean it's safe. Even if the weak spot is the human operator, the system interaction may in fact be causal to a disasterous outcome. Look at overriden autopilots and "human error" (a term of diminishing value).
And I certainly am not willing to accept automation to achieve a sense of ease of operation (my logic is that I will want to confirm every action toward the desired outcome anyway).
Does this mean that an automated system (in the case of CCR solenoid, leaky valve or ADV) is inherently "bad" in my view? Absolutely not! It just means that I don't accept them off the bat.
On the contrary, my thinking leads me to the thought that they may well be very reasonable candidates for back-up systems. But as for the primary operation?
Five: I don't need an automatic boyancy valve to constantly adjust the volume in my BC. I don't need a leaky valve into my drysuit. Obvious to most, if I can't manage those systems, I should be doing "smaller dives" until confident.
If I'm running a breather fully manual (which is the backup to most electronic solutions anyway), I haven't my hands full. And if I do have my hands full, I can't dive anyway (BC/drysuit adjustments).
So the logic, for me, is do I want an automated system to be my primary and a manual to be my secondary, or the other way around?
For me, manually running an O/C platform with a CCR "plugin" while maintaining gas reserve to finish the dive on an integrated O/C, makes sense.
I think that, at least in terms of human/machine interface errors, a lot of risk is managed and diminished substantially, and the "hassle" is minimal.
The only thing is, a "solenoid can work deeper than a MAV". I don't know that I'll need to pull an aweful lot of 200m+ dives anyway, but if I do - do I really want to operate with no backup I expect to work, or a backup that I expect to work, but don't really love?
Such is my thinking as it relates to the OP question about perceived risks and my personal views on how to meet them.
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He did try using pure O2 rebrethers but toxed out. Cousteau probably never would have started diving if it weren't for a car accident. Georges Commeinhes would have beat Cousteau to it if Hitler hadn't interfered. Cousteau probably wouldn't have co-invented the Aqua Lung or gotten it to the international market if his father-in-law wasn't a director of L'Air Liquide. Interesting how things work out.
Scroll down to Post #2 and the "All the pieces were in place:" heading.
A Brief History of Diving (before 1943)
Edit: Cousteau could never have developed an eCCR because the enabling technologies weren't invented yet. Measuring O2 levels required a chemistry lab in those days. A paraeet maybe? Even if O2 sensors were available, what would he use to control them? Lead-acid batteries and vacuum tubes?
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