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Closed Circuit O2 Rebreathers and Training?
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When I followed my first scuba diving course, in 1975, the Cressi 57B ARO was the standard system used for most of the course.
The course was 6 months long and we got to compressed air OC systems only at the end, in the last month and in the dives at the sea.
The ARO was an excellent didactic tool to be used in the pool, as it forces the student to get complete and perfect control of breathing an buoyancy.
So I was certified for using it down to 10m, and after the certification I actually used it for 4 years, before giving up completely.
In the sea it is terribly dangerous, and here in Italy, where AROs were widely employed, we had a significant number of fatalities and severe accidents.
Fast forward 30 years, I ended up working for OMG, which had just been purchased by SIEL.
They wanted to ensure that their top military ARO rebreather, called Caimano (the evolution of the Castoro) was silent eniugh for not being detected by enemy's surveillance systems.
So they hired me as an acoustical consultant, and I had the possibility to use these modern ARO units both in their test pool at the Sarzana factory and at the sea, at Varignano, the base of Comsubin special force.
What a difference from the old Cressi ARO...
These modern units are not pendular (single hose) they use a loop circuit, allowing to breath "normally". Furthermore they provide automatic oxygen injection in the counterlung when you burn it, so you do not need to manually inject it.
Finally these units can also be used as semiclosed circuit rebreathers, with an additional Nitrox tank, allowing to reach depths down to 36 meters.
Actually Siel manufactures 4 different ARO models, including the old OMG Castoro C96. Here the links:
SIEL Advanced Sea System
SIEL Advanced Sea System
SIEL Advanced Sea System
SIEL Advanced Sea System
The course was 6 months long and we got to compressed air OC systems only at the end, in the last month and in the dives at the sea.
The ARO was an excellent didactic tool to be used in the pool, as it forces the student to get complete and perfect control of breathing an buoyancy.
So I was certified for using it down to 10m, and after the certification I actually used it for 4 years, before giving up completely.
In the sea it is terribly dangerous, and here in Italy, where AROs were widely employed, we had a significant number of fatalities and severe accidents.
Fast forward 30 years, I ended up working for OMG, which had just been purchased by SIEL.
They wanted to ensure that their top military ARO rebreather, called Caimano (the evolution of the Castoro) was silent eniugh for not being detected by enemy's surveillance systems.
So they hired me as an acoustical consultant, and I had the possibility to use these modern ARO units both in their test pool at the Sarzana factory and at the sea, at Varignano, the base of Comsubin special force.
What a difference from the old Cressi ARO...
These modern units are not pendular (single hose) they use a loop circuit, allowing to breath "normally". Furthermore they provide automatic oxygen injection in the counterlung when you burn it, so you do not need to manually inject it.
Finally these units can also be used as semiclosed circuit rebreathers, with an additional Nitrox tank, allowing to reach depths down to 36 meters.
Actually Siel manufactures 4 different ARO models, including the old OMG Castoro C96. Here the links:
SIEL Advanced Sea System
SIEL Advanced Sea System
SIEL Advanced Sea System
SIEL Advanced Sea System
Hi
I do have 3 oxy rb units. One c96 and two mk1 pendulum units.
it us a pleasure to dive with these units but the last thing I would do is to fin non stop doing nav.
As said before, co2 buildup mixed with high ppo2 is not a good idea.
If you want to stay above 6m taking your time to look around, these units are good. Otherwise, forget it.
I do have 3 oxy rb units. One c96 and two mk1 pendulum units.
it us a pleasure to dive with these units but the last thing I would do is to fin non stop doing nav.
As said before, co2 buildup mixed with high ppo2 is not a good idea.
If you want to stay above 6m taking your time to look around, these units are good. Otherwise, forget it.
scubascan
New
Ah interesting!
telemonster
Contributor
Hello!
Backstory
--------------
Sooo. I actually have a Castoro C96 from O.M.G. in Italy, which I think is the unit you are talking about. I saw it years ago on RebreatherWorld.com, thought it looked cool and had an ebay search. I will post pictures of it this evening.
Similar to the LAR V, they are super simple and seem to never come up for sale. On the LAR V side, the ones that do seem to be in military collectors hands.
Finally one of them popped up and I managed to buy it. The prior owner used it to escape the country of Dubai when they revoked his passport. He had a submarine manufacturing company and was lured to move it over to Dubai. At first things went well then the relationship soured. I was just after the CCR, but ... well he wrote a book about it and included an autographed copy of his book: https://www.amazon.com/Escape-Dubai-Herve-Jaubert/dp/0929915941
Training
------------
With regards to training. CCRs are a nightmare because they're all mostly similar, with some small differences. But each unit has individual training and most instructors can only teach a unit or two. So no luck getting C96 training in the USA.
I read Mastering Rebreathers by Jeffery Bozanic. Especially the 100% o2 stuff.
I read the manual for the C96, which is pretty complete. It's about 36 pages.
O.M.G. CASTORO C96 PRO OPERATION AND MAINTENANCE MANUAL Pdf Download | ManualsLib
There is a guide to diving the thing recreationally. Apparently they sell it over in Italy and it's easy to deal with over there. Less lawyers maybe.
LOOK at the NOAA maximum daily O2 exposure limit chart! That is a downside, you don't get the scrubber run time, you get O2 CNS limits.
After I read up on it, I just took it to a pool and dove it. 100% o2, new sorb, fill and breathe the bag out to atmosphere 3 times and should be good to go. Bubble check it. Don't go below 20ft (Salt water? Fresh water?) and don't exceed daily o2 CNS limits. And well, watch out for signs of o2 CNS toxicity.
Had to get the tank hydro'ed and o2 fills.
What's it like?
--------------------
Mine is an older unit, the modern one you are looking at might be different/better.
Later I actually took training for Hollis Prism 2 that I got used (fistbump to StuartV) so that is my main comparison. I have maybe 50-70 hours on the Prism 2 CCR now and maybe 6-7 on the C96.
The Prism2 is way more enjoyable, especially WOB. Rigging the little C96 is strange, as you need a bunch of weight to counter it on a belt or something. Depending how you are in the water (true with any CCR) the WOB changes, but the C96 to me was a bit rough in a few different positions. I need to try it again, and it makes me wonder how the Optima front mount is better. Maybe I need to wear the C96 higher.
My C96 has a tactical BCD strange thing that came with mine, and it has a tiny little tank for filling the BCD. That tiny tank does not have a burst disk therefor is not able to be hydro'ed in the USA. I have transfilled it to a few hundred PSI (way less than 500) but usually don't. The tactical BCD thing sits kind of odd and comes way up behind the head. Crotch straps yoinking my junk pretty hard too.
The buckles on the unit are from ITW Nexus, and the sizing is all kinds of non-standard. 40mm for the bottom, but the top ones are 45mm or something and I couldn't find those. The original pics show two simple straps one around the neck one around the waist. I want to try that without the BCD, or be able to clip it off to a backplate/harness maybe. Difficult to rig.
I needed a special fill adapter for mine that came from the UK. You have to remove the O2 gauge and fill it through that fitting! I posted on here years ago where I got that thing. That took a lot of work to find, it goes from DIN to the O2 gauge port.
On my unit there is no ADV, and there is this valve on the tank that has a push button for manual O2 addition, and the gauge. This assembly has a tiny leak on mine. The company via email has been pretty unresponsive with regards to selling a rebuild kit for this, and not sure if the local shop would take on such a thing. Last time I took it in a pool I just turned the knob on/off. But parts is a headache. Company doesn't seem to respond to emails (to me at least.)
The idea that it's cute and a super streamlined design which originally caught my eye... Hmmm. Setup and teardown is definitely still involved, including disinfecting it. The hoses feel REALLY high quality, I will say handling those after the Prism2 it's like "maaan little hoses you are way nicer with your silky high quality feel."
I don't know the scubber size or duration off the top of my head, but it might be quite a bit more to dive than a normal tank. This is all dependent on your shop. Some of them charge real high for 100% o2 fills. Then the sorb is about $160 a jug and you might get 8 fills out of one.
ALSO. My unit I think is a military version, but a yellow bagged recreational one popped up via a pawn shop on eBay about 4 years ago. So someone else out there in the USA has one.
Backstory
--------------
Sooo. I actually have a Castoro C96 from O.M.G. in Italy, which I think is the unit you are talking about. I saw it years ago on RebreatherWorld.com, thought it looked cool and had an ebay search. I will post pictures of it this evening.
Similar to the LAR V, they are super simple and seem to never come up for sale. On the LAR V side, the ones that do seem to be in military collectors hands.
Finally one of them popped up and I managed to buy it. The prior owner used it to escape the country of Dubai when they revoked his passport. He had a submarine manufacturing company and was lured to move it over to Dubai. At first things went well then the relationship soured. I was just after the CCR, but ... well he wrote a book about it and included an autographed copy of his book: https://www.amazon.com/Escape-Dubai-Herve-Jaubert/dp/0929915941
Training
------------
With regards to training. CCRs are a nightmare because they're all mostly similar, with some small differences. But each unit has individual training and most instructors can only teach a unit or two. So no luck getting C96 training in the USA.
I read Mastering Rebreathers by Jeffery Bozanic. Especially the 100% o2 stuff.
I read the manual for the C96, which is pretty complete. It's about 36 pages.
O.M.G. CASTORO C96 PRO OPERATION AND MAINTENANCE MANUAL Pdf Download | ManualsLib
There is a guide to diving the thing recreationally. Apparently they sell it over in Italy and it's easy to deal with over there. Less lawyers maybe.
LOOK at the NOAA maximum daily O2 exposure limit chart! That is a downside, you don't get the scrubber run time, you get O2 CNS limits.
After I read up on it, I just took it to a pool and dove it. 100% o2, new sorb, fill and breathe the bag out to atmosphere 3 times and should be good to go. Bubble check it. Don't go below 20ft (Salt water? Fresh water?) and don't exceed daily o2 CNS limits. And well, watch out for signs of o2 CNS toxicity.
Had to get the tank hydro'ed and o2 fills.
What's it like?
--------------------
Mine is an older unit, the modern one you are looking at might be different/better.
Later I actually took training for Hollis Prism 2 that I got used (fistbump to StuartV) so that is my main comparison. I have maybe 50-70 hours on the Prism 2 CCR now and maybe 6-7 on the C96.
The Prism2 is way more enjoyable, especially WOB. Rigging the little C96 is strange, as you need a bunch of weight to counter it on a belt or something. Depending how you are in the water (true with any CCR) the WOB changes, but the C96 to me was a bit rough in a few different positions. I need to try it again, and it makes me wonder how the Optima front mount is better. Maybe I need to wear the C96 higher.
My C96 has a tactical BCD strange thing that came with mine, and it has a tiny little tank for filling the BCD. That tiny tank does not have a burst disk therefor is not able to be hydro'ed in the USA. I have transfilled it to a few hundred PSI (way less than 500) but usually don't. The tactical BCD thing sits kind of odd and comes way up behind the head. Crotch straps yoinking my junk pretty hard too.
The buckles on the unit are from ITW Nexus, and the sizing is all kinds of non-standard. 40mm for the bottom, but the top ones are 45mm or something and I couldn't find those. The original pics show two simple straps one around the neck one around the waist. I want to try that without the BCD, or be able to clip it off to a backplate/harness maybe. Difficult to rig.
I needed a special fill adapter for mine that came from the UK. You have to remove the O2 gauge and fill it through that fitting! I posted on here years ago where I got that thing. That took a lot of work to find, it goes from DIN to the O2 gauge port.
On my unit there is no ADV, and there is this valve on the tank that has a push button for manual O2 addition, and the gauge. This assembly has a tiny leak on mine. The company via email has been pretty unresponsive with regards to selling a rebuild kit for this, and not sure if the local shop would take on such a thing. Last time I took it in a pool I just turned the knob on/off. But parts is a headache. Company doesn't seem to respond to emails (to me at least.)
The idea that it's cute and a super streamlined design which originally caught my eye... Hmmm. Setup and teardown is definitely still involved, including disinfecting it. The hoses feel REALLY high quality, I will say handling those after the Prism2 it's like "maaan little hoses you are way nicer with your silky high quality feel."
I don't know the scubber size or duration off the top of my head, but it might be quite a bit more to dive than a normal tank. This is all dependent on your shop. Some of them charge real high for 100% o2 fills. Then the sorb is about $160 a jug and you might get 8 fills out of one.
ALSO. My unit I think is a military version, but a yellow bagged recreational one popped up via a pawn shop on eBay about 4 years ago. So someone else out there in the USA has one.
If I may add to @telemonster,
The C96 has two versions: one with a small metal canister (old OMG version, sold now by Sanosub) with 1.5kg of lime (need to be checked) and one with a larger metal-plastic canister @ (2kg I think...) which is the OMG-Siel version.
Yes you can get it (or used to get it) with a yellow cover
For diving rec (not military with all the stuff), I think the best way is not to use the tactical vest. Just around your neck and a belt at the waist. Best also to get rid of the original tank-bypass system and get a 1.5 L alu tank with a normal valve, a normal reg with a gauge on a short hp and a short lp hose linked to a MAV(and into the bag) and that it.
Before going into the water, you empty the bag and your lung and inject oxy (at the beginning, it is better to do it at least times but with experience, if you empty your lung correctly, once is enough). As you go down you will need to manually add oxy in order to breath. Staying at the same depth, you will feel that after few minutes, having metabolised the oxy, you start to sink indicatiing you need to add more oxy. It fact it needs time to get the feeling for this but after a few dives, like a lot of skills, it becomes second nature.
At the beginning, the problem is weighting as the tendency is to have too much weight. Personnally, with a 3min, I used to have 7 kg because I was putting too much oxy in the bag. Now 3kg is enough and with a DS, 6 is fine.
I also dive in a flat position and as you dive to 6m max, you can also play with the bag to get your trim and bouyancy "perfect"
If i don't have my small tank, I put a male bcd end on one port of the MAV port and plug a bcd hose from a reg on a SM s40 or whatever I can get.
I think complete manual oxy rb is a good way to learn the instrinsicalities of diving rb but of course you must be well aware of ppo2 limits and not forgetting to flush the unit regularly.
So, as an instructor for these units is not available, to find a mentor is the best option.
But again for the OP, forget these machines doing non-stop nav
The C96 has two versions: one with a small metal canister (old OMG version, sold now by Sanosub) with 1.5kg of lime (need to be checked) and one with a larger metal-plastic canister @ (2kg I think...) which is the OMG-Siel version.
Yes you can get it (or used to get it) with a yellow cover
For diving rec (not military with all the stuff), I think the best way is not to use the tactical vest. Just around your neck and a belt at the waist. Best also to get rid of the original tank-bypass system and get a 1.5 L alu tank with a normal valve, a normal reg with a gauge on a short hp and a short lp hose linked to a MAV(and into the bag) and that it.
Before going into the water, you empty the bag and your lung and inject oxy (at the beginning, it is better to do it at least times but with experience, if you empty your lung correctly, once is enough). As you go down you will need to manually add oxy in order to breath. Staying at the same depth, you will feel that after few minutes, having metabolised the oxy, you start to sink indicatiing you need to add more oxy. It fact it needs time to get the feeling for this but after a few dives, like a lot of skills, it becomes second nature.
At the beginning, the problem is weighting as the tendency is to have too much weight. Personnally, with a 3min, I used to have 7 kg because I was putting too much oxy in the bag. Now 3kg is enough and with a DS, 6 is fine.
I also dive in a flat position and as you dive to 6m max, you can also play with the bag to get your trim and bouyancy "perfect"
If i don't have my small tank, I put a male bcd end on one port of the MAV port and plug a bcd hose from a reg on a SM s40 or whatever I can get.
I think complete manual oxy rb is a good way to learn the instrinsicalities of diving rb but of course you must be well aware of ppo2 limits and not forgetting to flush the unit regularly.
So, as an instructor for these units is not available, to find a mentor is the best option.
But again for the OP, forget these machines doing non-stop nav
The only agency I know of which still certifies divers on 02 CCR is TSA (Trimix Scuba Association) in Italy. It seems to make sense, ARO was an Italian invention, was it not ?
Your well being might be worth the cost of the training and of the journey to Italy. What's your opinion about that ?
Your well being might be worth the cost of the training and of the journey to Italy. What's your opinion about that ?
Geo7
Contributor
I sympathize with your goal and fascination of a small O2 rebreather, and occasionally have thought of it for photography. I'd just like to add a word of caution since I noticed your comment "barely underwater, with a clear and quick bailout right above me".
Even these seemingly simple rebreathers are tricky. The military spends weeks on training, unlike days in recreational SCUBA. Traditionally combat swimmers are seen in the media wearing an inflatable vest that lifts the head out of the water when actuated. Buddy pairs are tethered together by ropes (ok, part of their training is at night without dive lights). You'd think that is exagerrated safety, but they have lost divers.
Even at only 6 meters depth (20 feet) you breathe oxygen at a PO2 of 1.6 which has civilian time limits (NOAA: 45 mins) that are shorter than what the military does. Tech divers usually avoid exercise at those oxygen partial pressures (use during deco). Convulsing and blacking out from oxygen toxicity might or might not give a warning. Susceptibility one day may be different from another. Blacking out from lack of oxygen from misuse or lack of discipline ("purging procedures") also gives no warning. Carbon Dioxide poisoning (Hypercapnia) from a wet scrubber or misused scrubber (easy to do), has reportedly left people so incapacitated that they almost drowned in knee-deep water and had to be dragged out by bystanders. Finally, even a caustic cocktail is no fun. Some experienced rebreather divers on this forum (I am not) take a lookout person when they dive CCRs in the pool, and that should tell us something.
What I want to say is this: Even though I have been trained on electronic mixed gas rebreathers, I personally would not pick up an O2 rebreather and assume my previous training qualified me to use pure O2 models at those PO2s and while swimming. Different machine, and also a different kind of diving. The attachments might further highlight the complexity of using O2 rebreathers. There is also a german book by a former combat swimmer about diving O2 CCRs which is excellent.
So if you are going forward with this you need two things IMHO: a good buddy to go along with you, and preferably a rebreather instructor who has been in the military and dove those models. There are a few, Tom Mount, Joseph Dituri, Leon Scamahorn, Paul Haynes and surely more.
Y'all are good scuba buddies! I am more than impressed by all the contributions and knowledge here!
But just so you know, if I'm not mistaken (click on his username) our OP hasn't been back since he first posted. He may not have seen any of this.
Still, good info for lurkers!
But just so you know, if I'm not mistaken (click on his username) our OP hasn't been back since he first posted. He may not have seen any of this.
Still, good info for lurkers!
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.The only agency I know of which still certifies divers on 02 CCR is TSA (Trimix Scuba Association) in Italy. It seems to make sense, ARO was an Italian invention, was it not ?
Your well being might be worth the cost of the training and of the journey to Italy. What's your opinion about that ?
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.
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