A Comparison-contrast Of Available Rebreathers

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One suggestion if I may:

Add a link to this thread at the end of the last part so people can leave comments, ask questions etc. :)
 
So I didn't want to let to much time go by without mentioning a new rebreather that is starting to get a lot of attention:

From reading up on the the new Juergensen Marine, Inc. Hammerhead CCR it’s looking pretty exciting. It appears to be the veritable Rubik’s cube of eCCR’s. Various iterations of the HH electronics have been used in quite a few rebreathers over the years. All reviews I’ve seen look true to the claim that all those years of experience have culminated in what is poised to be one of the top rebreathers.

There are two scrubber options, both are radial design, the smaller one is half the size of the larger. It has both back and over the shoulder counter lung options. It takes a variety of tank sizes. It's electronics configuration allows for multiple options in a variety of failure modes. It can be run in manual mode with a constant mass flow valve or in automatic injection mode by an electronic set point controller, or both! It comes stock with a BOV (bail out valve). It has two independent handsets, each with integrated deco. It has a place for 4 cells, the three intended for the primary po2 system and a 4th for a third party independent monitoring system. The head has a threaded port in place to make connecting a 4th cell monitor relatively easy. It comes with the DIVA style vibrating HUD, as is found on the Optima.

I'm most impressed with it's degree of modularity and redundancy. It looks like a lot of innovative thinking has gone into this rig to address a wide variety of preferences. I'm very much looking forward to hearing reviews from owners as the hours on the unit get racked up.
 
I'm adding this response from another thread, since it was a bit OT.

I agree, it is mostly mind set and habits. Unfortunately habits are not entirely voluntary. Most of the mistakes you could make are much more likely to be caught if you are flying manually, probably because the habitual monitoring interval required for running the system under normal circumstances coincides proportionally with what would be required to avert disaster if you made a mistake or if a malfunction occurred.

The exact opposite is true for an eCCR. A screw up on the diver's part or a malfunction creates a sudden and unforgiving problem that requires a monitoring interval that far exceeds that required under normal operating procedure. there is no positive feedback loop that entrains the appropriate monitoring interval... most of the times you space out while diving an eCCR there are no consequences and that gradually encourages complacency. Add diver error to that after many hours of flawless functioning and you have a recipe for disaster.

Also, around these parts there is a consensus that hypoxia is the main killer... a MFO on an mCCR gives you quite a po2 cushion. manual injection is simple and easy, a lot less scary than it sounded to me when I first started this adventure. It doesn't really make sense when you think about it, you just have to try it.

IMHO,
g



Can you point me to some hard data that indicates diver death caused by a failure of a rebreather? I know there are a couple of rather definate ones but you have to agree a vast majority of CCR failures were the result of the divers themselves, either in the pre-dive or properly responding to dangerous conditions. The safety issue between eCCR and mCCR has more to do with the mindset of the user than equipment itself.
 
Someday hopefully their will be an objective system in place so we can really examine the dynamics of each fatality but the point is really the same weather it's 150 to 1 or 124 to 8... the ratio is overwhelming either way and very hard to explain away. the KISS philosophy bears out in the numbers, while the "set point controller as safety net" does not appear to be.

When I started venturing into this 2 1/2 years ago I was convinced that the exact opposite would have been true. It really goes against one's natural inclinations that injecting manually would be associated with fewer fatalities, that you are apparently less likely to space out when the stakes are high enough. the mentality required for manual injection may even reduce the likelihood of making a fatal mistake in the first place even during set up. After owning and diving both systems, I have all the evidence I need to make a firm choice. manual monitoring and po2 maintenance requires that I check my po2 much more frequently than I could get myself to on an eCCR and i'm much more aware of the nuances of injection requirements with each stage of the dive.

all that said, just about any conclusions with respect to rebreathers are speculation. I've simply focussed my speculation on the area that I believe is most likely the culprit...but it all falls short of absolute conclusion. the likelihood that the above numbers are a coincidence seems incredibly remote to me but ultimately each person has to come to their own conclusions based on what little solid information they can get their hands on.

g



Your count is probably a bit off.. considering there have been at least 5 deaths on the voyager and 2 on the submatix.. The reports don't specify if they were in mccr or scr mode, but judging by the experience level and depths involved they were probably mCCR mode..

also the count you cite 150ish includes alot of scrs and unknowns.. a quick review shows at least 26 deaths on scrs
 
Someday hopefully their will be an objective system in place so we can really examine the dynamics of each fatality but the point is really the same weather it's 150 to 1 or 124 to 8... the ratio is overwhelming either way and very hard to explain away. the KISS philosophy bears out in the numbers, while the "set point controller as safety net" does not appear to be.

When I started venturing into this 2 1/2 years ago I was convinced that the exact opposite would have been true. It really goes against one's natural inclinations that injecting manually would be associated with fewer fatalities, that you are apparently less likely to space out when the stakes are high enough. the mentality required for manual injection may even reduce the likelihood of making a fatal mistake in the first place even during set up. After owning and diving both systems, I have all the evidence I need to make a firm choice. manual monitoring and po2 maintenance requires that I check my po2 much more frequently than I could get myself to on an eCCR and i'm much more aware of the nuances of injection requirements with each stage of the dive.

all that said, just about any conclusions with respect to rebreathers are speculation. I've simply focussed my speculation on the area that I believe is most likely the culprit...but it all falls short of absolute conclusion. the likelihood that the above numbers are a coincidence seems incredibly remote to me but ultimately each person has to come to their own conclusions based on what little solid information they can get their hands on.

g


The MCCR vs. ECCR fatality comparison is somewhat premature. Comparisons need some track record of reliable data. Additionally, and as mentioned, some questions regarding fatalities cannot never be quantified. Some factors to consider, and in no particular order:

* Number of divers using said systems - huge variables here #MCCR vs #ECCR

* Years in operation. ECCR's had an earlier start/teething process, and start-up proportions of fatalities during the mid, to late 90's was high. Naturally instruction changed in response to # of fatalities and early trends.

* Monitoring and feedback devices present

* Prevailing environmental conditions - how tough are the conditions

* Mission - how tough are the conditions

* Unit design

* Quality of instruction

**Quality of diver (attitude and aptitude)

etc, etc. You can add more to the list, and I bet it's been batted to the point of insult on RB world. :D

I will acknowledge one point having dived both systems - MCCR does establish a routine mental, and near mechanical system of monitoring. That being said, this automatic form of vigilance should be present and instilled during the early days of instruction, and applicable to all form of RB diving. This means - if I ask any RB diver to manually fly their RB for the entire dive - they should be able too.

When I used an Inspiration in the UK, there had been 3-5 fatalities already. Very scary. The Wak Cis episode had occurred too. One thing I did in my training was monitor my PO2 constantly (every 1-1.5 minutes) & make sure that gases were injectable based on the early findings from these fatalities.

The HUD features that are/were present in the first production CIS, Megalodon and Hammerheads were extremely intelligent features.

One thing will occur, more MCCR users, more incidences.

Cheers.

X
 
The MCCR vs. ECCR fatality comparison is somewhat premature. Comparisons need some track record of reliable data. Additionally, and as mentioned, some questions regarding fatalities cannot never be quantified.

Lots of good points. I"m finding though that just about any conclusion is premature to some folks... this one is hard to refute, at least in my opinion and i'm not willing to wait around for facts that may never come. Using reductive reasoning is the next best thing we have to go on.


Some factors to consider, and in no particular order:

* Number of divers using said systems - huge variables here #MCCR vs #ECCR

It does make sense that there are more eCCR's out there, but as long as manufacturers keep the numbers to themselves, we are left to speculate and guess as to the real comparisons. I am personally appalled that the manufacturers are not more forthcoming. they put a lot of pressure on training agencies, maybe it's time for the training agencies to push back with a few demands of their own.

* Years in operation. ECCR's had an earlier start/teething process, and start-up proportions of fatalities during the mid, to late 90's was high. Naturally instruction changed in response to # of fatalities and early trends.

* Monitoring and feedback devices present

* Prevailing environmental conditions - how tough are the conditions

* Mission - how tough are the conditions

* Unit design

* Quality of instruction

**Quality of diver (attitude and aptitude)

etc, etc. You can add more to the list, and I bet it's been batted to the point of insult on RB world. :D

all good things to consider, and thankfully we don't need to resort to insult here to discuss this... I appreciate your non-inflammatory tone!

as for monitoring and feedback devices, conditions, level of task loading and attitude of diver:
the KISS has traditionally used some of the most basic and arguably not even that robust of monitoring systems and they are known for some common failures and still no deaths.

Since there is no mass tracking of stats on who's doing what type of dives with which rebreather, one will always be able to bring up the question of weather the dives being done on eCCR's are comperable to mCCR's. More and more, people are doing just about any kind of dive on mCCRs. I guess we just have to give it time to see if the numbers continue to bear out. Won't it be sad if postponing serious research on this results in more of some of the best divers perishing?

I'm not sure how much longer the industry intends to wait before giving a more serious look at the potential explanations for the massive difference in fatalities. I hate to think it could be that producing and selling eCCR's is so much more profitable that the industry would rather not know the answer.

Attitude of diver is a very good thing to look at. are mCCR's self selecting, attracting the particularly anal people? Maybe, but what I think is more important is the question of how the system of monitoring and maintaining po2 could be responsible for changing, or entraining, the attitude of any diver. it has certainly had an undeniable huge impact on my diving style. From what i've gathered so far, the effect of having to monitor and maintain is self limiting and just about any diver stands a better chance at mastering it adequately to deal with failures and screw ups that are someday inevitable. As I am constantly reminded of the effects of inadequate monitoring any time my po2 drops a bit below my ideal range, it seems that my overall degree of vigilance is reinforced, from setting up to breaking down the unit.

I will acknowledge one point having dived both systems - MCCR does establish a routine mental, and near mechanical system of monitoring.

a point of agreement!

That being said, this automatic form of vigilance should be present and instilled during the early days of instruction, and applicable to all form of RB diving. This means - if I ask any RB diver to manually fly their RB for the entire dive - they should be able too.

another point of agreement, but I'd go one step further in asking weather it's possible to instill the level of vigilance required by an mCCR in an eCCR, where one is, conversely, reminded every time they space out that the system has everything under control. To me it comes down to weather there is as an effective substitute for being forced to pay attention at regular intervals. Also, being able to fly manually on occasion is not the same as doing it all the time, in every mind state... on an mCCR your are practicing these life sustaining procedures all the time. It's hard to believe that such a level of practice would not result in better reflexes. an example: I put 100+ hours on an eCCR before switching over. I was astonished at how much I needed to add o2 on ascent initially when I started diving mCCR's. This may sounds ridiculous, sure I heard the solenoid going back when I dove eCCR, but having to do it myself over and over, must be better preparing me to deal with an emergency where I may either be ascending out of control or simply wanting to speed up my ascent and needing to rely more on habit to achieve adequate injection intervals.



One thing will occur, more MCCR users, more incidences.

Cheers.

X

I would have to agree here as well, and while I'm slow to conclusions, I've really put a lot of energy into studying this and I'm comfortable enough with my hypothesis to predict that the ratio of fatalities will continue along similar lines even as the number of mCCR divers seems to continue to expand exponentially.
 
Lots of good points. I"m finding though that just about any conclusion is premature to some folks... this one is hard to refute, at least in my opinion and i'm not willing to wait around for facts that may never come. Using reductive reasoning is the next best thing we have to go on.




It does make sense that there are more eCCR's out there, but as long as manufacturers keep the numbers to themselves, we are left to speculate and guess as to the real comparisons. I am personally appalled that the manufacturers are not more forthcoming. they put a lot of pressure on training agencies, maybe it's time for the training agencies to push back with a few demands of their own.



all good things to consider, and thankfully we don't need to resort to insult here to discuss this... I appreciate your non-inflammatory tone!

as for monitoring and feedback devices, conditions, level of task loading and attitude of diver:
the KISS has traditionally used some of the most basic and arguably not even that robust of monitoring systems and they are known for some common failures and still no deaths.

Since there is no mass tracking of stats on who's doing what type of dives with which rebreather, one will always be able to bring up the question of weather the dives being done on eCCR's are comperable to mCCR's. More and more, people are doing just about any kind of dive on mCCRs. I guess we just have to give it time to see if the numbers continue to bear out. Won't it be sad if postponing serious research on this results in more of some of the best divers perishing?

I'm not sure how much longer the industry intends to wait before giving a more serious look at the potential explanations for the massive difference in fatalities. I hate to think it could be that producing and selling eCCR's is so much more profitable that the industry would rather not know the answer.

Attitude of diver is a very good thing to look at. are mCCR's self selecting, attracting the particularly anal people? Maybe, but what I think is more important is the question of how the system of monitoring and maintaining po2 could be responsible for changing, or entraining, the attitude of any diver. it has certainly had an undeniable huge impact on my diving style. From what i've gathered so far, the effect of having to monitor and maintain is self limiting and just about any diver stands a better chance at mastering it adequately to deal with failures and screw ups that are someday inevitable. As I am constantly reminded of the effects of inadequate monitoring any time my po2 drops a bit below my ideal range, it seems that my overall degree of vigilance is reinforced, from setting up to breaking down the unit.

a point of agreement!

another point of agreement, but I'd go one step further in asking weather it's possible to instill the level of vigilance required by an mCCR in an eCCR, where one is, conversely, reminded every time they space out that the system has everything under control. To me it comes down to weather there is as an effective substitute for being forced to pay attention at regular intervals. Also, being able to fly manually on occasion is not the same as doing it all the time, in every mind state... on an mCCR your are practicing these life sustaining procedures all the time. It's hard to believe that such a level of practice would not result in better reflexes. an example: I put 100+ hours on an eCCR before switching over. I was astonished at how much I needed to add o2 on ascent initially when I started diving mCCR's. This may sounds ridiculous, sure I heard the solenoid going back when I dove eCCR, but having to do it myself over and over, must be better preparing me to deal with an emergency where I may either be ascending out of control or simply wanting to speed up my ascent and needing to rely more on habit to achieve adequate injection intervals.


I would have to agree here as well, and while I'm slow to conclusions, I've really put a lot of energy into studying this and I'm comfortable enough with my hypothesis to predict that the ratio of fatalities will continue along similar lines even as the number of mCCR divers seems to continue to expand exponentially.


Terrific points and I appreciate your observations and hypothes(es). I promise to add more shortly. Sadly, the family dog had to do some rebreathing of anaesthetic gas today and I am waiting around for him to come to.

Cheers,

X

Quick note: I feel the same as you do with respect to educational "push back". Putting product before instruction makes very little sense , other than the economics of moving units and selling "instruction." As a CCR instructor I see safety as the paramount point(s) regarding UW instruction and manufacturers should disclose details regarding their units, and possible connections/links regarding incidents that may have occurred on their units.
 
Just adding to the piece above...safety should be the focus of all rebreather education. Vetting a student is an important first part of the process, as is coursework which ensures a consistent level of proficiency. In my recent experience, the vetting and fulfillment of standards is somewhat variable. No surprise there as the pool grows, gets diverse and standards diluted.


MCCR accidents will grow as more users enter this niche of the RB diving, and as some push their units harder. I also believe that MCCR users are far more cognizant of the nuances in oxygen addition and their metabolism...which translates to being aware most of the time. ECCR guys can get complacent. I know I do when it comes to video work. This is why I choose to have someone supervise me, as I become myopic.

Since I dive all sorts of RB units I have no favorites. Each one does what its supposed to, and I try to keep pace with each of the units needs. I do fly the ECCR manually most of the time, as a result of using an MCCR. I think its good practice.

Additionally, the doggie came through with flying colors regarding his "rebreather" exercise.

X
 
ECCR guys can get complacent. I know I do when it comes to video work. This is why I choose to have someone supervise me, as I become myopic.

ECCR and video. ECCR allows me to shoot the way I used to do on open circuit, long shots with both hands on the camera. And I must admit, I do trust my HUD a lot. There have been situations where I wasn't able to look at my handsets for minutes. Was I complacent? Perhaps. The video certainly gets most of my attention. But I hope that either the HUD or other things like the buzzer, volume changes (I always keep minimal loop volume) or the solenoid not firing alert me in time.

I normally don't dive alone on CCR. Most of the diving/filming we do are wreck dives. When I'm filming a diver from behind, I don't want him to look back every 10 seconds. That will look unnatural on video. When I'm leading parts of the dive, I'm sometimes way ahead of my buddies to get far, medium and short shots. They can't really see me either because of my video lights. So, with a buddy is better than without one, but the buddy should not be overrated.
 
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