I would assume by how you died...
You look and find the loop hypoxic....
I would assume by how you died...
Deep_Six
CCRX Supporter
I think you've mentioned failed cells and multiple failed cells a few times recently. Is there something out there you've read/seen/know that shows that to be a common thing? I'd like to read up on that to frame your comments better.
Garth
Tunnel Vision
What I'm trying to say is that people die because there is a problem. Whether it be the diver, the ability for the diver to understand the cell issue or the divers ability to be situationally aware of the other malfunction in the rebreather.
I believe that the type of rebreather is less important as the situational awareness of the diver him/herself.
Regardless of MAV/oxygen cell type/location etc, the ability to be present in the current moment is above all the most important factor in my opinion.
The point I would like to make would be aside from the most that but rather the likelihood of failure and the response/speed necessary to remove the danger.
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I believe that the type of rebreather is less important as the situational awareness of the diver him/herself.
Regardless of MAV/oxygen cell type/location etc, the ability to be present in the current moment is above all the most important factor in my opinion.
The point I would like to make would be aside from the most that but rather the likelihood of failure and the response/speed necessary to remove the danger.
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Deep_Six
CCRX Supporter
The diver can run the gamut from absolute weakest link to strongest link. The bitch of it all is that you only need to be the weakest link once...
The fastest way to mitigate a hypoxic loop is to have the O2 MAV on the inhale lung. Can't see any way to make it any faster than that - yet you seem to despise this choice. Even though hypoxia seems to be the cause of death for roughly 2x more divers than hyperoxia. If the ppO2 is 0.6 and dropping who the bloody hell cares if the next breath shoots up to 1.5 at your mouth when you lay on the O2 MAV with a bit of urgency? You aren't going to swing from passing out to toxing, just doesn't happen.
If the cells are bad then O2 MAV location is irrelevant. Regardless of location, if you lay on the O2 MAV at depth then perhaps CCRs aren't for you.
Mikwright
New Member
Which, is OK as long as that is 0(.)6 and not 6(.)0 because of a cell failure.
I'm not trying to argue, because I agree with you and would probably give the O2 a squirt, especially on the mCCR. O2 or dil, it still requires some thinking to diagnose.
Mark Chase
ATB=AlwaysTalkingBollocks
Cells are a very simple and for the most part reliable componant in a CCR
The failure mode of a cell is arguably singular in that it stops reading the PP02 accuratly
In my experiance this failure takes on three modes;
1: temperature compensation error / faulty cell
This failure mode is mildly irritating in that the cell reaction times are odd and the readings slow to settle but its realy not life threatening if you ensure the cell reading against a known gas
2: "Burn Through"
My own name for it but basicly just before a cell fails it starts to read high and fast. Like a last hara before it dies. I have swaped out cells on predive checks / asembly meerly because getting from 0.21 -1.0 has happened much more quickly than the other two cells and they read high in ambient pure 02.
Shouldent be fatel because the chances of it hapening to all three cells at exactly the same time and in a uniform way are so small as to be right up there with shark attack.
3. Current limited cells
Cells are burnt out and can no longer display the higher end PP02s Or cells have failed and cant display high PP02
SHouldent be fatel as long as ou confirm cells in a known gas and spike ocasionaly to ensure they can read above displayed PP02. Again uniform failure across three cells is unlikley especialy if stagered cell rotation is employed as part of the service program.
So in short stop worrying about cells and worry a LOT about how you as a diver aproach diving a CCR.
The only thing that worries me about diving a CCR is C02 because i know it will nark me to the point I will be incapabule of dealing with the situation. I dont know any way arround it except to watch my work load work of breathing and to make sure i dive within my prefered scrubber limits
PP02 is a non event in terms of risk to my health just so long as I stick to the rules
I am about 90% good at sticking to the rules and the other 10% of the time I have just been lucky.
Only diferance between me and some is I admit that and I dont blame the unit in any way for my own stupidity.
ATB
Mark
Garth
Tunnel Vision
So the fastest way is the best. I'm not sure I buy that either. I guess I just don't agree with the design choice and find it more disturbing that so many are okay with it. The fact that more divers die from hypoxic situations than from hyperoxic is irrelevant when you consider that the better option to mitigate BOTH of those situations is to use an appropriate diluent that raises PPO2 to the proper level while at depth.
I guess I can agree with anything for the first 20ft though...
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Deep_Six
CCRX Supporter
We need one of those dead horse emoticons....
My last diver has just arrived so we're outta here but I will try to get back to this one in the evening.
Didn't you start this thread as "you look down an find the loop hypoxic?"
At least one published paper finds that more divers die of hypoxia than hyperoxia. Having a hyperoxic breath (one) seems to be the focus of your paranoia about having the O2 MAV on the inhale lung. Or do you have some other concern?
The fastest way to get more O2 in your mouth and mitigate your own hypothetical scenario that this thread is supposedly about is to inhale it on the next breath, not flush the whole loop with some (potentially) modestly higher O2 content gas.
Nevermind that your strategy doesn't work at all when you have dil for a 600ft dive and you are at 20ft with this hypoxic loop. Looking down and seeing you're at a ppO2 of 0.6 at 20ft and then doing a dil flush with 10/50 is going to make your loop more hypoxic not less. So doing "anything" within the first 20ft is probably not a good idea.
Getting trimix trained and not trying to redesign CCRs to avoid fantasy risks are good ideas.
Deep_Six
CCRX Supporter
No one is trying to sell you anything Garth. Your comments are fairly trollish in nature and it seems you're not really trying to understand differing views/design choices. You've made up your mind and that's fine. Why start this thread then? At least you should have named it more honestly...maybe something like "I hate the Meg and Meg divers are dumb". Or "O2 cells are evil and Megs suck".
Anyway, I'm beat but just a few disjointed ramblings...
- The O2 MAV orfice, the counterlung, the T-piece and the corrugated hose, when you think about it, pretty much act like a miniature nitrox stick. Even setting aside the physics <gasp!>, just the rough and tumble path that squirt of O2 has to take is more than enough to mix it. Not like we're talking about injecting a massive 3l dose of O2 into the lung. If you still doubt that gases mix that rapidly, try this experiment. Put your snot locker in close proximity to the meaty solenoid found at the aft end of every Mk 1 Mod 0 canine (located just under the base of the tail) and wait till Rover 'injects' some gas...voila, that hits your olfactory receptors almost instantly! And that's mixing in an unconfined space with a clear, non-turbulent path between said solenoid and your snot locker. Same thing happens with that old lady at the mall...shoot, lots of times you can smell the cheap perfume BEFORE she gets to you.
- The most correct response for a hypoxic loop in most circumstances but not necessarily all is a dil flush. I have yet to read where someone has recommended otherwise. Well, some folks do advocate bailing immediately, which might also be the most reasonable course at the time. In neither of these scenarios does it matter diddly squat where O2 is injected into the machine. Of course, another option is to inject a healthy dose of O2 instead but this is an option on any unit, not just the Meg. The fact that it may occur further away from your mouth is irrelevant as to whether it happens to be the most correct course of action for those circumstances. Recall that my 'hypoxic event' was not on a Meg. However, I felt that injecting a phat shot of O2 was the most appropriate response to keep my dumb ass alive given my circumstances. Worked out anyway, even though it took longer to get a dose of higher O2 gas.
- O2 cells are the weakest link in the CCR proper. However, understanding the fault modes of O2 cells, the timely use of cell checks throughout the dive (not just during assembly) and the proper interpretation of those data, in conjunction with the most appropriate corrective actions (if required) for the present dive parameters will carry the day. There is no getting around the divers role in this OODA loop. I don't want my rebreather to act like it was built by Airbus. You, the 'pilot', have to know your rebreather and dive it...don't let the rebreather dive you.
Anyway, in the vernacular of today's youth... I'm out, peace!
Mark Chase
ATB=AlwaysTalkingBollocks
Mr Six I say again
It can take a good couple of flushes to purge a loop and if your flushing with 10/50 and the loop is hypoxic it may take a while to get into breathable gas.
The fastest way to increase PP02 is surely inject 02.
So on reflection i am not so sure dill inject is a good idea.
Having thaught about it a while I conclude bailout or 02 inject. 02 inject being the safer option IMHO
I only want a scinario that works in ALL situations
ATB
Mark
It can take a good couple of flushes to purge a loop and if your flushing with 10/50 and the loop is hypoxic it may take a while to get into breathable gas.
The fastest way to increase PP02 is surely inject 02.
So on reflection i am not so sure dill inject is a good idea.
Having thaught about it a while I conclude bailout or 02 inject. 02 inject being the safer option IMHO
I only want a scinario that works in ALL situations
ATB
Mark
Garth
Tunnel Vision
My intent was not to be a troll so if I have done so I will no longer continue this discussion. I feel like there has been quite a few good posts on here and we have determined a few things.
1: there is variability amongst failure response to a hypoxic situation (some people bailout immediately, some flush with diluent, some add oxygen and others do a combination of more than one of these).
2: There is variability among training standards among different rebreathers (some are taught to respond to failure in different ways).
3: We all accept the risks and love our Rebreathers, cells, Counterlungs and all. Including myself. I love it and although I don't agree with what everyone has said on how they respond to failure I do appreciate the responses and dialog on the topic.
I enjoy the dialog as always and can't wait until my Meg arrives... (Wink, wink, everybody hug) hehe
Cheers,
Garth
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1: there is variability amongst failure response to a hypoxic situation (some people bailout immediately, some flush with diluent, some add oxygen and others do a combination of more than one of these).
2: There is variability among training standards among different rebreathers (some are taught to respond to failure in different ways).
3: We all accept the risks and love our Rebreathers, cells, Counterlungs and all. Including myself. I love it and although I don't agree with what everyone has said on how they respond to failure I do appreciate the responses and dialog on the topic.
I enjoy the dialog as always and can't wait until my Meg arrives... (Wink, wink, everybody hug) hehe
Cheers,
Garth
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kwinter
PITA
This depends on dil and depth, and is the whole focus of the other nasty thread. They are clearly related, which is my reason for frustration. If you are of the school that believes consistency is key, and diving hypoxic dil all the time (even for shallow dives) is better than changing diluent based on the dive plan, then it can not be argued that a dil flush is always the best response to a hypoxic loop. At least Mark is being consistent. ALWAYS diving with hypoxic dil and ALWAYS reacting to hypoxic loop by adding O2.
Well, maybe not ALWAYS.............
Deep_Six
CCRX Supporter
I understand your statement to mean a procedure that works in all scenarios for the way YOU dive your unit and not a universal procedure. Obviously, diving a hypoxic dil shallow changes the equation. Like you, I spent a long time on a KISS so I'm certainly not 'afraid' of injecting O2 at depth or anywhere else.
This thread has been rather manic in it's focus which is why I've tried to caveat so many of my comments and stated earlier that a hypoxic dil necessarily changes the response tree (not in those words though). Hypoxic dil and presumably hypoxic bailout gas places an even greater responsibility on the diver to not fall behind in unit management.
I guess I'm not a huge believer in universal responses because they are usually chock full of caveats. Keep your SA high, stay inside the OODA loop and truly understand your unit and it's idiosyncracies.
Best,
Tony
DSix36
Well-Known Member
I almost always dive with 10/50 dil. I was trained to use a dil flush prior to any bailout in one unit and to bailout prior to any "loop repair" on another unit.
I have not yet had the unfortunate opportunity to find my po2 low enough to be immediately deadly or dangerous, but I am sure that my response would be the same same as if merely very low. I would add O2, it would probably mean really laying on the button damn near to the point of a flush.
Like Mark and others have mentioned, high po2 will not render you dead instantly and I have no fear of an extremely high po2 for a short period of time.
This goes against both of the training protocols that I was taught, but I would like to believe that I understand what is happening and that I have become a thinking diver that is capable of making competent decisions. I know this statement leaves me wide open to________
I have not yet had the unfortunate opportunity to find my po2 low enough to be immediately deadly or dangerous, but I am sure that my response would be the same same as if merely very low. I would add O2, it would probably mean really laying on the button damn near to the point of a flush.
Like Mark and others have mentioned, high po2 will not render you dead instantly and I have no fear of an extremely high po2 for a short period of time.
This goes against both of the training protocols that I was taught, but I would like to believe that I understand what is happening and that I have become a thinking diver that is capable of making competent decisions. I know this statement leaves me wide open to________
I've always followed the mantra that above 6m i inject O2. Below 6m, its dil.
Dave cooper years back made the point that if its that bad, you might only have seconds of usable consciousness and suggested both buttons at once. I can see the logic in that. You get the thing life sustaining then sort out the fine details after.
Dave cooper years back made the point that if its that bad, you might only have seconds of usable consciousness and suggested both buttons at once. I can see the logic in that. You get the thing life sustaining then sort out the fine details after.
