Electronic vs manual CCR

[Simon Mitchell]

Hi Ben,

I am surprised anyone with "Dr" as a title is niave enough to think there are enough divers and deaths on CCR to perform statistical analysis!

I don't think Andrew is around these boards, so I think it is appropriate for someone who knows him and is familiar with his data to clarify some of the issues. There are several points:

First, Andrew has never presented a "statistical analysis" in the true sense of the expression.

Second, he is scrupulous about pointing out the limitations of his data when he presents them.

Third, his efforts to bring clarity to this issue have resulted in the ONLY relevant "data" that exists (with all its weaknesses acknowledged). Prior to Andrew's initiative all we had was wholly unsubstantiated but often repeated speculation that had resulted in it becoming an article of faith that mCCRs are safer.

Fourth, what Andrew has done is simply to compare what we know of the prevalence of the two types of units in the diving community with the proportion of deaths known to have occurred on each respective type. The prevalence in the community data comes largely from several surveys that have polled divers about what sort of unit they use (I think one of them was on RBW and I cannot remember how many respondents there were). Obviously if 80% of the deaths occur on eCCRs and 80% of rebreather divers use eCCRs then the apparently high mortality on eCCRs is not surprising. This is essentially what he found: that prevalence in the community and representation in mortality data were closely matched. It is nothing more than that, and Matthieu (above) says it is not enough to sway his opinion - fair enough. But these are the only relevant figures we have to inform the debate. It is therefore difficult to support an argument that one sort of rebreather is safer than another... based on what we currently know.

Of course, the poop slide could be appended to the end of this post too!

Simon M

 

[GLOC]

Dave having sat through Andrew's presentation I can assure you that his presentation does not draw any firm conclusions at all. He shows that there just isn't the evidence to do that, but using all of the available data that is out there (DAN, BSAC, DiverMole, RBW datasets, DeepLife etc) to show generalities.

I know that Andrew is putting a paper together for SPUMS and it is posing some issues because it is not as robust as most papers should be, indeed I believe that this is one of the major conclusions, there isn't enough quality data.

At RF3, TDI, IANTD and ANDI showed some certification data and I know that PADI are going to share their's in the same bundle too. This is a good start but there are too many commercial interests to make this as robust as it should be. Indeed, I have some concerns over the presentation made by TDI, ANDI and IANTD about where the market is going given the stats that they presented.

Until people start to accept that everyone makes mistakes and treat divers who make mistakes as equals, then we are not going to get this data. I know of one CCR fatality that didn't even get reported to BSAC even though the DO went to the funeral. If we are in this current situation, the system is broken.

Something that has come up in my own research (from the recent survey) is that 10 years ago Margaret St Ledger Dowse (Comparative data from 2250 male and ... [Aviat Space Environ Med. 2002] - PubMed - NCBI - you can also download it if you google but I am not going to hyperlink to the document - I got into trouble the last time!) presented analysis of approximately 2250 divers in the UK. The median age group was in the 31-40 category (~43%), with 41-50 being the next highest (~26%) and over 50s around 12%. From my survey, this is now 29% in the 31-40, 33% in the 41-50 and 24% older than 50 years old. From my results, the over 40s now make up more than 57% of divers - these divers are likely to have more disposable income and able to afford CCRs but they are also likely to be those more susceptible to non-diving medical issues which are accentuated by hyperbaric conditions.

Regards

 

[Ben Field]

When it comes to arithmetics, keeping a watchful eye, or fine control, I'll take the computer every day of the week. A computer does not get bored or tired. It does not forget. It doesn't feel pity, or remorse, or fear.

Sorry, got carried away here

No need to apologies, its an interesting area- one in which I totally disagree with you

If you spend millions on software development you sometimes generate safe systems, the massive errors seen in complex and expensive systems like airliners, nuclear reactors, spacecraft and medical equipment is testament to this. These systems are also constantly monitored by technicians, have regular servicing and upgrades (most commonly software) yet still there are recalls (Toyota just recalled 3million cars for example, throttle mapping I believe?)

Now, you want to design a rebreather and sell it to a niche market with low volumes for less than $10K, you will expect no regular servicing to done, poor monitoring and random battery supply. This whole rebreather will be designed and built by a small team, sometimes less than 5 people.

Given the massive gulf its not surprising the software and hardware of many CCR's need such careful handling

My observation has always been that its easier to make a simple thing work than a complex thing, when a simple thing is equally capable of the task why bother attempting the complex thing at all?

It's not me saying it. It's medical device manufacturers. It's Boeing and Airbus. It's the engine manufacturers, most likely including the one in your car. Along with your ABS brakes.

EXACTLY- All systems that are prone to failure, even Boeing admit they have no reference of the number of errors in many of their airliners base code, IIRC the 747 a few years back was claimed to have 100 errors in the first million lines alone! (This is why super critical software has line limitations for there to be a reasonable chance of manually triple checking the code)

Yes, my car has ABS and electronic everything, don't trust the thing one inch! There is talk of drive by wire steering in the next couple of years- be interesting to see how that goes down.

FWIW I much prefer cycling, fully manual control. More reliable than my car too but that's hardly fair since I drive a Renault

I don't think Andrew is around these boards, so I think it is appropriate for someone who knows him and is familiar with his data to clarify some of the issues. There are several points:

First, Andrew has never presented a "statistical analysis" in the true sense of the expression.

Second, he is scrupulous about pointing out the limitations of his data when he presents them.

Third, his efforts to bring clarity to this issue have resulted in the ONLY relevant "data" that exists (with all its weaknesses acknowledged). Prior to Andrew's initiative all we had was wholly unsubstantiated but often repeated speculation that had resulted in it becoming an article of faith that mCCRs are safer.

Fourth, what Andrew has done is simply to compare what we know of the prevalence of the two types of units in the diving community with the proportion of deaths known to have occurred on each respective type. The prevalence in the community data comes largely from several surveys that have polled divers about what sort of unit they use (I think one of them was on RBW and I cannot remember how many respondents there were). Obviously if 80% of the deaths occur on eCCRs and 80% of rebreather divers use eCCRs then the apparently high mortality on eCCRs is not surprising. This is essentially what he found: that prevalence in the community and representation in mortality data were closely matched. It is nothing more than that, and Matthieu (above) says it is not enough to sway his opinion - fair enough. But these are the only relevant figures we have to inform the debate. It is therefore difficult to support an argument that one sort of rebreather is safer than another... based on what we currently know.

Of course, the poop slide could be appended to the end of this post too!

Simon M

Thanks Simon, to be clear I was replying to gallathans summary rather than the original presentation. Your summary is alot less conclusive (rightly so).

FWIW my own (highly unscientific) research into CCR "near misses" yielded an entirely expected result. 80% of the incidents where diver led (forgotten, mistakes etc, nothing to do with type of unit) most common of that (60% IIRC) was forgetting to turn on, connect, refill or some other issue with the O2 supply. That was again a tiny data set, 100-ish incidents from 90 divers.
My impression is that the fatal incidents probably conceal a similar truth, that a large % of accidents are co*k-ups.

FWIW I believe CCR's in general are considerably less safe than OC, both MCCR and ECCR are equally dangerous but the dangers are different and you have to be more of a moron to hurt yourself on a manual- I don't think that means is safer

Again, poop slide should perhaps preface this whole site :naughty:

 

[tufty]

well I was going to post something inciteful, but having been informed I dive one of the most unreliable ccr's out there:cuckoo: I think I'll just go and sulk, go diving (reliably) and enjoy myself on my eccr (that I occasionally run manually on ascent because its easier):juggle:
:moon:

 

[emmbee]

Well, it's true enough that more complex software tends to mean exponentially increasing costs, but thankfully dive computer software is extremely simple.

I am aware of (some) constraints placed on critical software, but I do not know of any line limits. For one thing that would be idiotic since any software engineer will be able to halve such a count by taking shortcuts, at the price of making it more difficult to understand.

The point stands that software is better than me, human being, at keeping tabs on what's happening. That's the point everyone who had serious thoughts about it agrees on (see examples).

Also, whereas a device requires proper design, proper manufacturing, and proper maintenance to function, software only requires proper design. Manufacturing is xerox. Maintenance, barring bugs (as opposed to upgrades), is nil (well, okay, there's radiation/cosmic ray interference or EPROM/flash decay, if you're really into that).

The device itself, the computer that is, can fail. I'm not aware of anyone monitoring cells at depth using an analog voltmeter, so you're already using such a device. Chip, LCD (or OLED) and all, subject to the same failures. Just with simpler software.

Which leaves the solenoid, and the cable joining it to the computer, as mechanical failure points.

Like I said, I didn't get to see Andrew Fock's presentation. Based on his other presentation about deco, which I did see, and drew some flak as well, I'm inclined to believe that his was a great assessment of scientific data, as opposed to "opinions".

Why is diving and mCCR just as safe as eCCR then, when I think the machine isn't? Dunno. Maybe the training compensates. Maybe the study didn't take into account the natures (i.e. depth) of the dives. Maybe the dive profiles allow for suboptimal ppO2 pressures. Maybe this is all just dredging in the statistical noise. Maybe, maybe.

Enjoy the diving.

Cheers,

Matthieu

 

[Dave Sutton]

I'm not aware of anyone monitoring cells at depth using an analog voltmeter, so you're already using such a device.

Cheers,

Matthieu

To the above, some of us do... Mark-15's, early Prism Topaz, and Cis Lunar Mk-5 all monitor pure analog millivolts straight from the cells. First two use old fashioned jeweled millivolt meters... With a needle..

Everything else you write is absolutely dead right. Well done.



Dave


.

 

[Mark Chase]

^^^^ What Don said.

The entire mCCR ethos originated with the KISS, in an era when civilian eCCR control systems sucked. Homebuilt KJ systems built on a kitchen table masquerading as "factory" products that barely worked, a death rate on the early Inspirations that was shocking, old analog averaging electronics on a few Mark-15's, the never-working CCR-2000, and the hugely complex Cis Lunar rigs that nobody could afford. In that paradigm the mCCR system was a breath of fresh air... It actually worked and you understood what it was doing.

Nowadays, with solidly reliable eCCR controllers available, mCCR's are a quaint throwback. Flying a hybrid rEvo is easy, as is flying a KISS, but they are just holdovers from a mindset formed when most controllers were utter crap. I ought to know, I've owned every rig described above, and the controllers were pathetic. That's all changed.


Dave


.

So explain recent deaths on the Poseidon? Arguably the most advanced and most safety focused unit on the market.


Because of age, previous medical conditions and stupidity, there will always be deaths in diving, regardless of OC MCCR SCR or ECCR.

If one has to examine ECCR on the basis that it provides life support when the diver screws up, then its the safer system. If however you look at ECCR in the light of the fact it makes divers switch off mentally and reduces there control of the dive to breath in breathe out, then they are very dangerous.

I am of the opinion that none of the CCR deaths that have occurred are the fault of the unit.

In my opinion we are taught to monitor the unit at all times and we are given the tools to overcome all issues arising from diving a CCR down to the option to bailout on to an adequate gas supply to end the dive.

But still hundreds of dives have died.

MCCR cant fix everything but it can take away the option for divers to ignore what their units are doing. And that fixes quite a bit.

I started out ECCR with a Inspo Classic and Hammer head units and then moved on to the KISS.

Moving over to the kiss made me realize I was kidding my self when i told people i was monitoring my unit properly.

I didn't want to go back to ECCR but due to some strange marketing choices from JJ i ended up on one. At first i can say i was just a vigilant as i was on the KISS but after two years of faultless performance on the JJ i am aware that my attention span has slipped back dramatical.

The statisticians can say what they like. The MCCR units with no automated life support, no buzzers and no flashing lights, should be considerably more dangerous than automated units with compelx warning systems. But they are not and in fact of the only two deaths i know of on the KISS one was illness and the other was a diver who panicked in a cave.

As I said MCCR cant fix everything.

 

[anarchista]

To the above, some of us do... Mark-15's, early Prism Topaz, and Cis Lunar Mk-5 all monitor pure analog millivolts straight from the cells. First two use old fashioned jeweled millivolt meters... With a needle..

You can give a better simpler solution, just galvanic oxygen sensors meet voltage, directly proportional to the partial pressure of oxygen.
In addition, people who use analog meters can evaluate the system constants time rate. Analog to digital converter technology with 16-bit quantization does not bring new value.
A controls P PI, PD, PID were known long before Elektrolung.

"IS-MIX is a new semi-closed rebreather from Interspiro based on the well-proven concept of ACSC and DCSC systems which have been in operation for over 30 years and have an excellent track record. These forerunners have been used under active service conditions to 150 meters and in simulator conditions to 450 meters."

Interspiro IS-MIX
The design implemented in a NATO (meeting in Istanbul 2011).
Mechanical structure CRABE is proposed Aqua Lung Military.

rc greet

 

[Mark Chase]

You can give a better simpler solution, just galvanic oxygen sensors meet voltage, directly proportional to the partial pressure of oxygen.
In addition, people who use analog meters can evaluate the system constants time rate. Analog to digital converter technology with 16-bit quantization does not bring new value.
A controls P PI, PD, PID were known long before Elektrolung.

"IS-MIX is a new semi-closed rebreather from Interspiro based on the well-proven concept of ACSC and DCSC systems which have been in operation for over 30 years and have an excellent track record. These forerunners have been used under active service conditions to 150 meters and in simulator conditions to 450 meters."

Interspiro IS-MIX
The design implemented in a NATO (meeting in Istanbul 2011).
Mechanical structure CRABE is proposed Aqua Lung Military.

rc greet

Is this not just another PSCR?

How can it do a single diluient / drive gas from the surface down to say 100m?

ATB

Mark

 

[WFO]

Now, you want to design a rebreather and sell it to a niche market with low volumes for less than $10K, you will expect no regular servicing to done, poor monitoring and random battery supply. This whole rebreather will be designed and built by a small team, sometimes less than 5 people.


EXACTLY- All systems that are prone to failure,

The point stands that software is better than me, human being, at keeping tabs on what's happening. That's the point everyone who had serious thoughts about it agrees on (see examples).

The device itself, the computer that is, can fail. I'm not aware of anyone monitoring cells at depth using an analog voltmeter, so you're already using such a device. Chip, LCD (or OLED) and all, subject to the same failures. Just with simpler software.

What does it matter if it is an analog voltmeter, if you are using a microprocessor to digitise the signal then another one to light the blocks on an LCD... still a digital signal. They are more robust than analog.


But these systems are only as good as the information they are fed and the actions they can take, look at the cell condensation issues on some units, can fool the computer into thinking everything is perfect. Or if somebody forgot to turn on the O2. The software solution to that would be some complicated pain in the arse unit like the sentinel and the argument just comes back to personal choice.

Personally I'm going for swagelok valve and a "dumb" handset and HUD. Simple reason I can't justify splashing a thousand quid on a shearwater when I could go diving.

 

[anarchista]

Is this not just another PSCR?

How can it do a single diluient / drive gas from the surface down to say 100m?

IS-Mix is SCR CMR, a different family of SCR.
http://www.interspiro.com/_downloads/99993B01 - IS-MIX Product Folder_Lweb.pdf
The SCR SMS deal with problems such as constant ppO2 and only 2 gases on board. Range HAHO up to 100 m
In one embodiment, the gas I have only one on-board and oxygen chemically accumulated.
http://bazy.uprp.pl/patentwebaccess/patentImage.aspx?id=4696529&numer=-1

greet rc

 

[GLOC]

Mark makes an interesting point about 'dependency' on automatic systems.

There is plenty of research, especially in aviation and other High Reliability Organisations, where just because automatic systems are really reliable (but not 100% perfect) the operators become accustomed to it working correctly and not practicing the emergency procedures, or even recognising unusual circumstances. Look at AF447 for a very recent example of this. I have a recent incident report of a CCR diver who had a significant number of hours on their unit and had been diving it very regularly for 10 years or so but had only ever bailed out a couple of times in that period. In the incident in question he really struggled with bailing out and setting the handsets up to deal with an OC ascent. Simple things but not practiced, they become a little more complex. (He was solo so didn't have someone to help, he also nearly switched to a hyperoxic mix because he was narc'd but fortunately the cylinder was switched off).

This was the point I was trying to make at RF3.0 when the discussion of more automation is a better thing came up. In the main, yes, but with more automation and as more complex scenarios require more contrived circumstances for a failure to occur, we (mainly the training agencies) need to be more thorough in developing complex problem solving scenarios for training (either initial or continuation) during or at least discussing them in a more public arena. These potential scenarios might not come up very often (you'd hope they'd been designed out) but they will do and operators need to get as much feedback as possible from everyone in the community. The manufacturers are unlikely to promote it as this would open themselves up for criticism from users who don't understand the limitations of the industry in which they are a consumer of.

Regards

 

[Mark Chase]

Mark makes an interesting point about 'dependency' on automatic systems.

There is plenty of research, especially in aviation and other High Reliability Organisations, where just because automatic systems are really reliable (but not 100% perfect) the operators become accustomed to it working correctly and not practicing the emergency procedures, or even recognising unusual circumstances. Look at AF447 for a very recent example of this. I have a recent incident report of a CCR diver who had a significant number of hours on their unit and had been diving it very regularly for 10 years or so but had only ever bailed out a couple of times in that period. In the incident in question he really struggled with bailing out and setting the handsets up to deal with an OC ascent. Simple things but not practiced, they become a little more complex. (He was solo so didn't have someone to help, he also nearly switched to a hyperoxic mix because he was narc'd but fortunately the cylinder was switched off).

This was the point I was trying to make at RF3.0 when the discussion of more automation is a better thing came up. In the main, yes, but with more automation and as more complex scenarios require more contrived circumstances for a failure to occur, we (mainly the training agencies) need to be more thorough in developing complex problem solving scenarios for training (either initial or continuation) during or at least discussing them in a more public arena. These potential scenarios might not come up very often (you'd hope they'd been designed out) but they will do and operators need to get as much feedback as possible from everyone in the community. The manufacturers are unlikely to promote it as this would open themselves up for criticism from users who don't understand the limitations of the industry in which they are a consumer of.

Regards

Automation is a wonderful thing but the problem with the CCR market is its under financed in terms of r&d and testing.


Massive car giants like Toyota have failures on simple switches and electronic steering control components and this to me demonstrates the ultimate fallibility of electrical systems in harsh environments.


If NASA built a ECCR it would probably cost millions in testing and development but id probably trust it 95% to do its job

CCRs we dive are for the most part built in sheds by enthusiasts. APD is one step up from a shed and look at the problems they are having with their own design 02 cells and the teething problems with the Vision.

We simply can not trust such under financed and under resourced companies to provide due diligence.

I am fine with that. I don't see any problem on a CCR that can not be overcome or dived around with some logical thought. I expect my unit to kill me and that keeps me alive.

My problem is i am far more diligent on my computer Chair than i am in the water.

MCCR simply removes the option to be complacent. Pay attention or i guarantee you will die is a good way to make people sit up and take notice.

I am horrified when people say they don't trust them selves to dive a MCCR.

If you cant trust yourself to dive a MCCR then that mens despite the fact you 100% know its going to kill you you still get distracted and don't follow standard procedures.

So you fix your complacency by supplementing your interaction with the controllers of an ECCR?

And we wonder why people get in the water with the 02 off and die?


Dr Mike put forward the counter argument that we shouldent be punnished by death for just forgeting to switch on the 02?

OK i see that point and its a tough one to argue against.


In my mind theres two ways of looking at safety.

The unit with the fewest moving parts is the most reliable. Reliable = safe

The unit with the most automated safety features is the safest because humans are fallible: Automated = Safe


In my view the second statement is only true if the Automated systems are infallible. If electronics are fallible and so are humans, then KISS is a good principle to work on.




ATB

Mark

 

[GLOC]

Bang on, but I know of at least one manufacturer who is trying to engineer out the problems by automating some things to either prevent the diver from getting in the water without the system confirming that it is working properly or if they, engineer a solution that keeps them alive if they do jump in without the kit having done its 'pre-dive checks'.

Engineer out a problem, then train the operator to cover shortfalls in that engineering solution. But make sure you train your operator adequately to deal with the situation when the engineering solution will fail.

Regards

 

[Ben Field]

Automation is a wonderful thing but the problem with the CCR market is its under financed in terms of r&d and testing.


Massive car giants like Toyota have failures on simple switches and electronic steering control components and this to me demonstrates the ultimate fallibility of electrical systems in harsh environments.


If NASA built a ECCR it would probably cost millions in testing and development but id probably trust it 95% to do its job

CCRs we dive are for the most part built in sheds by enthusiasts. APD is one step up from a shed and look at the problems they are having with their own design 02 cells and the teething problems with the Vision.

We simply can not trust such under financed and under resourced companies to provide due diligence.

I am fine with that. I don't see any problem on a CCR that can not be overcome or dived around with some logical thought. I expect my unit to kill me and that keeps me alive.

My problem is i am far more diligent on my computer Chair than i am in the water.

MCCR simply removes the option to be complacent. Pay attention or i guarantee you will die is a good way to make people sit up and take notice.

I am horrified when people say they don't trust them selves to dive a MCCR.

If you cant trust yourself to dive a MCCR then that mens despite the fact you 100% know its going to kill you you still get distracted and don't follow standard procedures.

So you fix your complacency by supplementing your interaction with the controllers of an ECCR?

And we wonder why people get in the water with the 02 off and die?


Dr Mike put forward the counter argument that we shouldent be punnished by death for just forgeting to switch on the 02?

OK i see that point and its a tough one to argue against.


In my mind theres two ways of looking at safety.

The unit with the fewest moving parts is the most reliable. Reliable = safe

The unit with the most automated safety features is the safest because humans are fallible: Automated = Safe


In my view the second statement is only true if the Automated systems are infallible. If electronics are fallible and so are humans, then KISS is a good principle to work on.




ATB

Mark

:trophy: :nod: :thumbsup: :clap: :worship:

EPIC Post Mark, that should be a sticky if ever I saw one!

 

[anarchista]

If NASA built a ECCR it would probably cost millions in testing and development but id probably trust it 95% to do its job
...... .
In my view the second statement is only true if the Automated systems are infallible. If electronics are fallible and so are humans, then KISS is a good principle to work on.

Designer struggled long to try them, aversion to any change was huge.

KISS is not a good rule of thumb, a principle he could offer designer.
The inability to design a control system.

rc greet

 

[Walt Stearns]

Automation is a wonderful thing but the problem with the CCR market is its under financed in terms of r&d and testing.


Massive car giants like Toyota have failures on simple switches and electronic steering control components and this to me demonstrates the ultimate fallibility of electrical systems in harsh environments.


If NASA built a ECCR it would probably cost millions in testing and development but id probably trust it 95% to do its job

CCRs we dive are for the most part built in sheds by enthusiasts. APD is one step up from a shed and look at the problems they are having with their own design 02 cells and the teething problems with the Vision.

We simply can not trust such under financed and under resourced companies to provide due diligence.

I am fine with that. I don't see any problem on a CCR that can not be overcome or dived around with some logical thought. I expect my unit to kill me and that keeps me alive.

My problem is i am far more diligent on my computer Chair than i am in the water.

MCCR simply removes the option to be complacent. Pay attention or i guarantee you will die is a good way to make people sit up and take notice.

I am horrified when people say they don't trust them selves to dive a MCCR.

If you cant trust yourself to dive a MCCR then that mens despite the fact you 100% know its going to kill you you still get distracted and don't follow standard procedures.

So you fix your complacency by supplementing your interaction with the controllers of an ECCR?

And we wonder why people get in the water with the 02 off and die?


Dr Mike put forward the counter argument that we shouldent be punnished by death for just forgeting to switch on the 02?

OK i see that point and its a tough one to argue against.


In my mind theres two ways of looking at safety.

The unit with the fewest moving parts is the most reliable. Reliable = safe

The unit with the most automated safety features is the safest because humans are fallible: Automated = Safe


In my view the second statement is only true if the Automated systems are infallible. If electronics are fallible and so are humans, then KISS is a good principle to work on.




ATB

Mark

Thanks Mark. The perfect argument to end this argument. The comment that sends a cold chill down my spine is the one that I have heard from a few rebreather divers that manual is too time consuming to fly and they prefer to trust the electronics in a eCCR model. The one thing that I have learned from my experience with diving, camera equipment, boats any everything else that comes in contact with a marine environment is that anything that runs electronically also tends to be allergic to water.

 

[Ben Field]

KISS is not a good rule of thumb, a principle he could offer designer.
The inability to design a control system.

Sorry but you couldn't be more wrong!

KISS has a control system, its your Thumb, Brain and Arsehole- when your arse starts nipping at your undersuit you look at the displays and thumb the O2 if necessary- impossible to ignore it :hehehm: (Obviously you check far more often.... cough)

You can simulate it on your drive home- close your eyes on the motorway and see how long you can keep them shut without dying (thats ECCR in full manual mode) now imagine you are driving a train instead, you can't crash side to side but you might run into another train (alot less likely), so you can keep your eyes shut for longer.... but you will still die if you don't look.

ECCR is like going home in an automatic car, wonderful.... except the time your wife parks on your side of the drive and you get all the way home and die a firey death on your doorstep because the programmer didn't include a check for who parks where :crash:

 

[anarchista]

Sorry but you couldn't be more wrong!

Sorry no system is compared to the SCR of the family CMR.
Only information on levels ppO2, high maintenance.

rc greet

 

[Megangel1]

Bit confused,

If I assume my total loop vol is 18 Ltrs and my starting ppo2 is 1.3, then don't I have about 20 mins, (given my o2 consumption is 1ltr per min) before I'm in the danger zone of .16 ppo2 or less ?

If there is anyone here who can not manage to monitor their ppo2 at all during a 20 minutes period, then I wish them luck with their games of underwater Russian Roulette and feel very sad for their family.

OK so my deco plan is going to be crap unless I have ppo2 integrated into my computer, but seriously guys, is the maintenance of ppo2 the most critical factor in the mCCR versus eCCR argument?

Even during direct ascent, from depth and a starting 1.3ppo2, one is unlikely to go hypoxic before reaching the surface?

Again here, mCCR with CMF is not going to hold your ppo2 at 1.3 or even close, a working eCCR has a better chance.

As far as I'm concerned the whole mCCR versus eCCR is about as useful as
which color is best Blue or Green?

Need I say that mCCR versus eCCR argument/discussion has one rather key flaw, they both use the same generation of unreliable o2 sensors?

Flame on.