Closed Circuit O2 Rebreathers and Training?

[telemonster]

The tactical BCD thingy, Front. CCR clips onto the 4 clips, top two are slightly larger than bottom two. Bottom seem to be 40mm ITW Nexus, Top might be 45mm

Included carrying case. Has a padded panel as well. Silver things are the fill adapters I had to source from the UK.

Tactical BCD back, with tiny cylinder for BCD inflation (no burst disc)

O2 cylinder with the funky valve that I need rebuild kit for. Has SPG, manual injection button and bib for connection to bag

Unit with the cloth outer bag open exposing the loop. Nice mouthpeice, has gag strap. No flood protection.

View of the soft bag that goes over the unit. The waist belt was home made and included by prior owner, but the top one was not. It also had two smaller clips added at the top of the unit, possibly for the escape from Dubai

Another view of the kit

I didn't full assemble it but there is how the O2 cylinder usually sits.

 

[Angelo Farina]

@telemonster your unit looks to me as an OMG Caimano IV ARO, a top-range military-grade unit, including the additional BCD. The older Castor C96 does not have the external covering and the BCD.
If I am correct, your unit is something which was not planned to be sold for recreational diving, this is the unit employed by Italian Comsubin for deep ARO diving (a very dangerous practice, when you do not wash-out air from the system and instead start at the surface full of air, so at depth you breath some sort of Nitorox mixture).
Having a BCD is fundamental for this technique. With a standard ARO without BCD, going deep make you become negatively buoyant, and you have to inject a lot of oxygen for keeping your neutrally buoyant. If you inject too much oxygen you risk hyperoxia (oxygen toxicity).
Instead, with a BCD, you can use it for correcting the negative buoyancy without the need to inject too much oxygen in the loop. But if you exceed too much, you risk hypoxia. So managing properly your unit for deep ARO diving is very critical.
However, I envy you for getting this unit. It is something almost impossible to buy for a private owner, it is highly valuable.
I do not suggest that you ever attempt to use this "deep ARO diving" approach, and perhaps it was safer if I did not provide you with any information about this approach. The "safe" way of using your ARO unit is as follows:
1) remove the BCD and install just two nylon straps, one around the neck and one at your waist.
2) always wash entirely any air for the system and from your lungs, using the three-ways valve at the mouth piece: inhale with the valve opening to the loop, and exhaling with the valve opening outside. repeat until there is no more gas in the loop and in your lungs -then inject enough pure oxygen so that you can fully inhale - at that point you should be slightly negatively buoyant at the surface.
3) never exceed a depth of 6 meters, and breath air at the surface for 10 minutes every 30minutes of diving.
Although you have got a military-grade unit, which has been successfully employed in missions down to 30-35 meters, no one with a bit of mental sanity would do that for recreational purposes. Even Italian COMSUBIN incursors do not use this method anymore, as now they have another version of the Caimano IV equipped with a second Nitrox tank (back mounted on the BCD), which allows to operate in semiclosed circuit, which makes it reasonably safe to reach a depth of 36m without risks of hypoxia or hyperoxia.
Here the successor of your unit:

 

[JMBL]

Actually most diving schools affiliated with FIPSAS (the most ancient training agency in Italy, and one of the founders of CMAS) are entitled to make ARO courses. This document (in Italian) is the technical program for the course.
http://lnx.ferreasub.it/wordpress/wp-content/uploads/2012/11/ARO.pdf
And here the related manual:
manuale federale d'immersione con a.r.o. (fipsas) - Libreria del Mare
I have the FIPSAS diving license for ARO units, it entitles me to a max depth of 10 meters. I am also a 3-stars FIPSAS-CMAS instructor, and so I can teach ARO courses (albeit I did never do that).
The ARO diving license is not linked to any specific brand-model, so I am entitled to use ANY ARO unit.
I was trained to using it during my first OW course, the ARO was considered, at the time, the best scuba system for training new students, as it forces to get a complete control of breathing, buoyancy and trim.
Albeit using an ARO is significantly more complex and definitely much more dangerous than using an open-circuit system with compressed air, it is not as complex as using a modern CC rebreather. It is a very simple mechanical unit, with nothing to "tune", and just one very simple lever for injecting oxygen in the loop. There is a three-way valve at the mouthpiece, and that's all. A new student learns to use these two valves in half an hour, outside of the water. Once the student understands how to use the valves, he can dive into the pool, and psycho-behavioural training begins. It usually takes 3 to 4 months, going to the pool twice per week for a couple of hours, for becoming proficient in using the ARO and being allowed to use it in the sea.
The ARO training has significant similarities with the training for deep free diving: the goal is not to learn skills or to get confidence with the technical stuff, this takes much a shorter time. The idea is to "reprogram" a number of physiological automations, and to condition the brains of the student for self-checking his body's response to very low or very high ppO2, and very high ppCO2. There are no electronic sensors in the ARO, and a good ARO diver "feels" the composition of the mixture he is breathing. This is particularly true for deep diving with ARO (military corps use it down to 30 m, with the trick of leaving a "proper" amount of air in the lungs and in the loop before starting the descent).
Of course, deep ARO diving is even more dangerous. During my training, I was introduced to use this "air dilution" of the mixture down to 12m, and I am certified to a max depth of 10m, which is something that now is not taught anymore, and new ARO divers are certified only to a max depth of 6m, and breathing always pure oxygen (no air dilution in the loop).
I do not recommend deep ARO diving to anyone, I know that US Navy Seals do no practice this technique, and even at the COMSUBIN corp this technique is considered obsolete, as now they have the Caimano IV SC rebreather, which can be operated safely in semi-closed mode with a Nitrox tank down to 36m.

Thank you for the precision Angelo. I knew about FIPSAS Aro courses, but to the better of my knowledge they are now a rarity. I quoted TSA aro courses, because it's the only one I know about, which offered and openly advertised for.

 

[jale]

Regarding @telemonster s unit, it is not that rare as you can get one if you are a bit patient. There is one now for sale on an european site for ... 3000euros!!!
You can even get one direcly from the mfg if you ask nicely
What is rare is the military harness coming with it and @Angelo Farina gives a proper description of its usage. And as he says forget it: stick to 6m max.
Regarding official training, I think ISE has or had one.

 

[Blackfrogfeet]

OP, are you already qualified to dive O2 rebreathers within the military? Or you just Want to do it because it looks cool out? You said you're a Marine so I think they use LAR V? The units all function the same. Some have a T valve for automatic injection, some have a manual addition valve (bypass), some have both. No PPO2 monitoring and no bailout generally speaking.

Speaking as a Navy Diver, what I would do if I were you... because from your post it seems like you don't have too much experience (which I assume is why you are asking scubaboard for advice). Get civilian mix gas CCR that is small, lightweight, and easily convertible to an O2 rebreather. Something like a Triton, or a WA Sweet Deco. Do the full tech diver training pipeline (the bare minimum at least). OW>AOW>Intro to Tech/ Fundamental>Advanced Nitrox + Deco or similar > CCR Air Dil. This will get you some experience, let you build your skill capacity and expose you to new ways of doing things. Then you'll be able to make your own choice on how to go about O2 rebreather diving as a recreational diver.

 

[telemonster]

@Angelo Farina Much thanks for the info! It's like Antiques Roadshow Scuba edition!

I never dive the unit past 20ft, and I do purge the loop a few times first. Also, I do air breaks as you describe (I think I read about them in Mastering Rebreathers or from the NOAA/US Navy manuals) but will admit I think the last time I did that I was doing 5 minutes every 20 minutes or so but at 10ft deep or so. The only place I ever dive it is Lake Phoenix or in pools once or twice.

There is a guy on youtube who dives a Lar V deeper using a self calculated Nitrox mix, but I would never do that as there is no ppo2 monitor on it (and I don't plan to add one because I don't want to damage the originality of it.) I have a Prism2 eCCR for that kind of stuff.

I am worried though about getting a rebuild kit for the valve due to it leaking and the lack of response from the new owners of OMG.

Still working on finding the mating plastic quick release buckles for the top strap. ITW Nexus shows a 40mm and 50mm buckle, but I think the 50mm would be too big. Might order a pair just to see. Was hoping 1.5" on the top and 40mm on the bottom but not quite it.

Thanks for the info!

 

[telemonster]

Something like a Triton, or a WA Sweet Deco. Do the full tech diver training pipeline (the bare minimum at least). OW>AOW>Intro to Tech/ Fundamental>Advanced Nitrox + Deco or similar > CCR Air Dil. This will get you some experience, let you build your skill capacity and expose you to new ways of doing things. Then you'll be able to make your own choice on how to go about O2 rebreather diving as a recreational diver.

That is a whole lot of courses that for the most part still won't cover what is in the 15 page manual that comes with the C96 says about how to build and dive it

If OP is competent at reading he could use the US Navy diving manual, O2 CCR section. The PDF is free, not behind a paywall and has good information as well. OP could reference that.

Or just build his own for like $200.

 

[Geo7]

The ARO training has significant similarities with the training for deep free diving: the goal is not to learn skills or to get confidence with the technical stuff, this takes much a shorter time. The idea is to "reprogram" a number of physiological automations, and to condition the brains of the student for self-checking his body's response to very low or very high ppO2, and very high ppCO2. There are no electronic sensors in the ARO, and a good ARO diver "feels" the composition of the mixture he is breathing.

Thanks for your valuable insight!

This kind of information is not really covered in ECCR training, which is why I hesitate to recommend use O2 rebreathers without specific training for that kind of diving (i.e. excertion at higher PO2s). I know experienced CCR divers use them for deco, but I mean specifically swimming at PO2 of 1.4 - 1.6, as that is clearly outside the typical parameters in the common agencies.

 

[Angelo Farina]

That is a whole lot of courses that for the most part still won't cover what is in the 15 page manual that comes with the C96 says about how to build and dive it

Remember that your unit is a Caimano MK4 CDV PRO, not a Castoro C96. The two units are easily separated by the position of the valve. It is on the left in Castoro C96 (that's the "recreational standard" here in Italy) and it is on the right on the Caimano MK4 (that's the "military standard").
Here the data sheet of the Caimano IV:
https://divestore.ir/img/cms/OMG-MK4-CVD.pdf
Here the extended version, covering also the SC-Nitrox version:
Katalog | Manualzz

 

[jale]

Just to split hairs, it seems to me that telemonster's unit is not a MK4 as it doesn't have the ADV on the bag (or at least I don't see that) but a C96 with the large canister.
Can you, Angelo, confirm that and also that I said before about the two versions of the C96. One with a small metal canister sold now by Sanosub and the new version with a large canister (the one telemonster has...I think).
Or maybe, we have just the same name for different units...a bit lost right now