Is this IT?!

[SFLDiver3445]

At this point more people are being turned off by the high fatality rate of eCCR's (1%) than turned on by impressive electronics. The number of manual rebreathers being offered suggests a lot of salmon are figuring out that they don't need to swim up stream.

The injection of oxygen just may turn out to be the one thing that humans do better than machines.

Gill, one important point that not everyone may be aware of is the fact that with an eccr, such as my Optima, you do have the option of running the unit electronically or manually. So even if folks do have that concern, you can lock in your your setpoint lower (say 1.0) and manually maintain the setpoint higher (say 1.2), that way you have the best of both worlds - You maintain it manually, but if need be, the electronics will maintain the setpoint at a minimum of 1.0. Wasn't there a thread posted on RW the other day when a diver had an emergency and needed to assist another diver in distress on the surface, only to realize after, that he had over breathed his loop, but was too distracted to monitor and add gas - In that scenario, the backup electronics option would have addressed that scenario and avoided that divers near hypoxic event.

So even looking at the debate from your perspective, there are advantages to an eccr, even if you run it manually 100% of the time.

 

[Gill Envy]

Gill, one important point that not everyone may be aware of is the fact that with an eccr, such as my Optima, you do have the option of running the unit electronically or manually. So even if folks do have that concern, you can lock in your your setpoint lower (say 1.0) and manually maintain the setpoint higher (say 1.2), that way you have the best of both worlds - You maintain it manually, but if need be, the electronics will maintain the setpoint at a minimum of 1.0. Wasn't there a thread posted on RW the other day when a diver had an emergency and needed to assist another diver in distress on the surface, only to realize after, that he had over breathed his loop, but was too distracted to monitor and add gas - In that scenario, the backup electronics option would have addressed that scenario and avoided that divers near hypoxic event.

So even looking at the debate from your perspective, there are advantages to an eccr, even if you run it manually 100% of the time.

flying an eCCR manually is advocated even by one manufacturer, Leon at the meg hatchery. If the cause of fatalities on eCCR's is in fact the attitude of the diver and if it turns out that a critical aspect of that is not voluntary, then running manually on an eCCR may not turn out to have the critical effect on attitude/habit, enough to lower the fatality rate as low as a manual injection systems. It could be that thinking you have a safety net is what really leads so many eCCR divers to become complacent, but Time will tell.

from a convenience point of view, I found manual injection on an eCCR to be quite a bother as the injection rate required was significant. It was also just too difficult to convince myself to stick with it... I generally fell back into having the set point controller take over. Turns out that the injection rate on a well tuned mCCR is a lot less than an eCCR because of the assistance of the mass flow orifice, which is basically a safety net that still requires a maintenance mindset. When i'm at a constant depth it's only every so often that I have to add o2... if you have not gone through an mCCR cross over training and put significant hours on such a unit you might not know just how easy it is.

From a field servicability point of view I can say that the hybrid HH, which I believe is available on the optima (correct?) is a big step forward in allowing someone options to continue diving in the case of a set point failure. In terms of reliability for long trips to the middle of no where, that is a big step forward in the eCCR realm.

 

[Meng_Tze]

..... Diving an mCCR in an overhead environment where zero viz is a potential requires a HUD that reads actual po2, IMHO. I've been in water I can't see my guages in (just this weekend) and I could still see my HUD and maintain my po2 just fine. I even went so far as to test just how poor the vis could be and found that in the worst case scenario, since I have a detachable HUD, I can press it against my mask if I find myself in pea soup. You've probably seen the video:The Shearwater HUD in Pea Soup...Zero viz! - Rebreather World
But if you have not used a manual system under such conditions I can see how it would stir up irrational fears and make you think that only an automated system would work in such cases. That said, i'm not a cave diver and perhaps there are other ways that an mCCR would not fit the job but so far I'm not hearing complaints from mCCR cave divers and they appear to be living to tell about it and even having fun!

I have said this on RBW as well, in an overhead environment, a HUD is THE most valuable tool on a RB. Regardless of type of RB. I was glad you dispelled (pea soup) most of the irrational discussions going on about absolute zero vis and exits.

 

[Meng_Tze]

flying an eCCR manually is advocated even by one manufacturer, Leon at the meg hatchery. If the cause of fatalities on eCCR's is in fact the attitude of the diver and if it turns out that a critical aspect of that is not voluntary, then running manually on an eCCR may not turn out to have the critical effect on attitude/habit, enough to lower the fatality rate as low as a manual injection systems. It could be that thinking you have a safety net is what really leads so many eCCR divers to become complacent, but Time will tell..

You do have a good point here. But I do not think that time will tell. We will never know what the cause was for an accident concerning 'running a unit manually'. Not unless we have a 'flight recorder type of system. Yes people are animals of habit, if a habit is maintained it becomes stronger. If it is retrained, in cases of stress, people default to old habits.

If the training we do to instill the correct habit focuses on just that, we would default to the correct habit.

I.O.W, if we teach eCCR divers to run their units manually from the beginning, would they 'fall back' on the auto injection, or instinctively prevent the this from triggering? We do teach in many occasions to use the unit as injecting things for you, in an emergency (solenoid failure) run it manually. We habitually expect the system to inject for us.

THIS is where I think a large root of the issue is......

 

[Gill Envy]

I.O.W, if we teach eCCR divers to run their units manually from the beginning, would they 'fall back' on the auto injection, or instinctively prevent the this from triggering? We do teach in many occasions to use the unit as injecting things for you, in an emergency (solenoid failure) run it manually. We habitually expect the system to inject for us.

THIS is where I think a large root of the issue is......

that is an interesting thought. Perhaps there should be a key to unlock the automatic set point controller in mod2, like some computers use for trimix. I really don't want to sound like some kind of proselatizing ludite but manual injection forces a person to learn the subletes of po2 change with changes in metabolism, depth etc, like nothing else can. I think learning manually on an eCCR initially is a really good idea, maybe for the first 100 hours or so.

The irony is that I see something like the Mark VI as a unit for very advanced and well trained divers who really need it to reach their goals, not beginners... for people who have a strong grasp of what is going on under the hood so that they can deal with the inevitable.

If it's introduction turns out to save lives and meet the needs of the masses then I'll happily eat these words.

 

[Meng_Tze]

And the really nice thing is that we can have this debate without detractions and personalities getting in the way. Thanks for that (to all). We both know that things can be a bit different in other places.

 

[SFLDiver3445]

And the really nice thing is that we can have this debate without detractions and personalities getting in the way. Thanks for that (to all). We both know that things can be a bit different in other places.

Yes, even though some of us appear to have diverging opinions about the degree of risk associated with eccr's, and about the future direction manufacturers will opt to take when designing future rebreathers, it has been a pleasure sharing viewpoints with such educated and respectful members of this forum!

 

[digital_steve]

noob comment below:

awesome... a closed circuit RB that is designed to be used within recreational limits. I love the idea of RB diving and want to do it eventually... but i can't see myself spending 7 hours at 110m to justify a RB purchase.
Initially i figured that when i was ready to go down the RB route (long time away, if ever) that i would go mccr... so i'm looking forward to reading more about this unit as it develops!

 

[almitywife]

noob comment below:

awesome... a closed circuit RB that is designed to be used within recreational limits. I love the idea of RB diving and want to do it eventually... but i can't see myself spending 7 hours at 110m to justify a RB purchase.
Initially i figured that when i was ready to go down the RB route (long time away, if ever) that i would go mccr... so i'm looking forward to reading more about this unit as it develops!

DS, hubby has a MEG and he only dives rec limits with it, and Dave H also (he has a KISS)

cheers

 

[digital_steve]

I knew i'd get caught on that L!
I should've mentioned that i'm not a photographer either... which is a very valid reason to get a RB