CCR Diving
Closed Circuit Rebreather (CCR) diving is a great way of diving but does have serious consequences if one is to violate the rules and procedures. Failure to do so might prove fatal. The CCR Diver course is an intense training program with large potential for frustration.
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The Machines
Each and one of the CCR Rebreather units from all the different manufacturers have two things in common. They recycle the breathing gas and effectifly remove Co2 (Carbon Dioxide) out of the recirculating breathing gas, and that the metabolized oxygen needs to be replenished either electronically or mechanically.
The Co2 absorbent is one of the key ingedients why Rebreathers work. Without Co2 absorbent (Sofnolime, Sodasorb, Extend Air) the Co2 that is produced as a waste product of our metabolism would be recirculate and be reconsumed, building up to intolerant and toxic levels. The propper changes of absorbent as well as staying inside manufacturer limits for absorbent duration is paramount to survival.
There are two different types of Closed Circuit Rebreathers on the market in regards of how the oxygen is injected and controlled in the Rebreather.
Electronically contolled CCR's have electronics built into the unit that measure the oxygen content in the breathing loop via oxygen sensors and will inject oxygen via a solenoid magnetic valve into the loop when user established setpoint values are not reached, thus bringing up the oxygen content in the loop back to user setpoint value and replenishing the metabolized oxygen.
Mechanically controlled CCR's have some electronics located in the Po2 readout located either in the handset or within the lid, and oxygen sensors. The replenishment however is done mechanically with constant flow injection and mechanically top up of oxygen by the diver with manual injection in order to bring and keep the Po2 at user selected setpoint.
Examples of electronically controlled CCR are the APECS Megalodon, O2ptima, Prizm Topaz, Cis Lunar, Inspiration, Evolution and OuroBuro.
Examples of mechanically controlled CCR are the Sport KISS and Classic KISS, Megalodon COPIS, IDA 72 and Submatix.
Buoyancy
Buoyancy is one of the most crucial skills in CCR diving. It provides the diver with a stable position to run lines, do tie off's, work with reel’s and pass easy through the water column.
Neutral buoyancy in a horizontal position with the legs up provides the CCR Diver with a streamlined and balanced profile while that particular position does protect the cave or wreck environment. What looks to us solid may be fragile speleothems, coroded superstructure or soft silt that can be agitated or broken with one uncontrolled touch of the hand or fin. Divers must be able to turn in a horizontal position, maintaining the horizontal position and depth without touching anything. While this requires practice it requires dedication for reef, cave or wreck preservation as well.
Mental considerations
A mental conditioning is vital for survival with a positive attitude for survival, with an understanding of the inherent risk associated with CCR diving, the willingness to strife for perfection in the art of CCR diving, the willingness to practice emergency exercises again and again until they become second nature. CCR diving is potentially not for everyone but for experienced divers willing to make an effort and these divers will be rewarded with some of the best diving on this planet, and a truly unique experience.
Commitment
The commitment needed for CCR diving goes beyond the time spend in the water but does include serious challenges to one self physically and mentally. The rewards are great and satisfying. Enrolling in a CCR diving course is a step into a new world.
Long term commitments do not only include the investment for the proper training needed to dive a particular Closed Circuit Rebreather safely. The financial commitment includes the equipment needed for this type of diving, the necessary life support equipment and the diving to come, to continue and practice what was learned during the training program, not to get rusty but to practice and practice again.
Training
In today’s world a variety of Rebreathers are available for the avid CCR Diver. Rebreathers are usually used to extend gas volume in remote locations, cave diving in the beautifull caves of Mexico or wreck diving applications where the needed gas volumes are not feasible to carry. Personal preferences and logistics dictate the choice of a particular unit. Most divers will choose a path that before CCR diving the diver has to be trained and experienced on open water diving and then can expand on rebreather technique and technology with an experienced CCR Instructor.
Few divers choose to take the initial and following training on Rebreathers and never take a single breath on open circuit SCUBA. But it can be done.
In order to learn CCR diving propperly a training program has to be completed either in stages or in whole, with considerable amount of time to be invested learning and repeating new diving skills and procedures. Your commitment and resolve will be tested here through intense training days filled with awesome diving experiences.
The level of Advanced Nitrox Diver is a prerequisite in order to enroll into a CCR Diver course. If you do not have previously done your Adv. Eanx course we can combine both training programs into one.
A minimum of six complete training days is required to complete the training neccecary for the basic or Mod. I CCR Diver.
Certification cards will be issued through IANTD
Bailout
Bailout is the alternate path to the surface if our Rebreather does not work anymore, for any given reason such as flood, not trusting it anymore or electronics failure. The CCR Cave Diver has a variety of scenarios and approaches that will get him back to the surface safely. The minimum gas that needs to be carried by the team is the volume needed to get 1 ½ divers back to the surface.
Team approach may work in most cases but it does not factor in team separation. I believe that having and major Rebreather problem and due to that major problem in the cave environment we may create bad or zero visibility, that could be resulting in a team separation is not something I personally would like to leave out of the equation.
As the individual approach is allowing to have each diver sufficient gas to bring himself to the surface, plus a margin of reserve the student and later CCR Cave Diver has a larger gas reserve. During post training dives this can be practiced and then expanded upon to further penetration and team bailout approach.
The whole bailout concept needs to be understood by the student in terms of not having all the time in the world anymore when on open circuit bailout, as well having to do potentially some 25 - 30 % more decompression due to falling Po2´s on the way up, depending on dive profile. Teaching a CCR Cave Course without proper bailout planning capability to the student is nothing else then giving the kid a loaded gun.
A long 5 or 7 foot / 1.5 or 2 meter hose on bailout tanks is a must and the deployment of the long hose from the always open bailout tank must be well practiced during safety drills. That will be a life saver and in some environments the only way to deal with a failed CCR in the cave. Handing over the stage in a fluid motion while sharing gas now on o/c and being under time and mental pressure will only lead to further problems, delays and stress. The hand over and sharing of the 7 foot hose, and not the hand over of a stage tank will be the key to some real emergencies. However, the hand over and exchange of bailout tanks in-between divers must be well rehearsed to enable proper execution in case the skill is needed in earnest.
The balancing of bailout gas volume within the team, within all present bailout tanks must be followed in either 1) team approach because the needed volume is split up in-between the team members and the out of CCR diver need their gas to make it back to the surface or the 2) individual approach to not breathe the bailout tank totally empty and loose all redundancy when still with other team members. Larger gas supplies are present with the individual approach, even when diving as a team allowing for delays exits such as restrictions, zero visibility, potential team separation and increased RMV.
When talking about furthest point of penetration o/c bailout versus right before deco bailout it is the furthest penetration that would be most problematic, as the divers still have to do the exit out of the overhead environment and then do the decompression. As we are fortunate enough to talk about cave diving and not ocean drift diving we are able to stage the deco gas at the cave entrance, but having sufficient bailout gas traveling horizontally through the cave will be the trick. Potential air hogs who go CCR to have more time in the cave still need to sling them large bailout tanks or they going to be running out of bailout gas. Taking a bailout tank without proper volume planning is like Russian roulette, and must not be done.
Besides opting for o/c bailout a different options is present as Jochen Hasenmaier, Olivier Isler and the Wakulla II team went to CCR bailout for at least two reasons. First gas volume and the ability to carry it, drag and the like, second is time pressure of diminishing gas supplies and associated stress levels translating in errors and elevated RMV. Open circuit, a SCR or CCR can be used as bailout to bring us back to the surface in case of unit malfunction.
The bailout planning will bring with it the change of breathing gas and Po2, and along with it changing decompression times and gases needed to finish the warranted decompression. We need to take submersible bailout tables with us underwater in order to recalculate potential changes in dive plans as long we stay on our CCR. Submersible tables need to be designed for the breathing gases used during proper function of our CCR as well as the o/c bailout gases we may use. Planning dives with deco planning software including the calculation bailout scenarios and to deep and long profiles, and having them on a slate would be ok when diving known caves and profiles.
The other bailout way in terms of breathing gases would be o/c - c/c dive computers either wired into the loop with a separate sensor, or not, that can and must be changed when going from c/c to o/c in a bailout scenario. Diving with only one of such computers has no redundancy. Bailout gas volume calculations are a must and done separate to insure sufficient breathing gas volumes.
-Bailout Valve or BOV
It has happened that a diver managed to get in the water without Co2 absorbent in his unit, despite checklist and all that. As they went down at about 20 feet / 6 meters the diver was breathing uncontrolled due to exertion and higher PCo2. The dive partner realized what is going on and urged the student to switch to o/c. The unit was not equipped with a BOV. The diver was not able to make the switch as he was not able to hold his breath for even a split second to do the switch over. They went to the surface and they lived to tell the story.
With a BOV the diver would have been able to switch from his CCR to his o/c bail out without a problem. Additionally the other diver could have intervened and help the affected diver.
I believe that if I decide to go off my CCR then I am off and want to go to something that is not connected at all to my CCR. Most BOV are connected to the inboard dilluent tank. With the limited volume offered by the onboard diluent tank the BOV is just a step in-between, to get off the loop and then onto the seperate bailout tank. Take a breath or three then go on to your o/c bailout stage, which is a completely separate life support system with precalculated po2 and gas volume, and you know it’s going to work.
I have seen some divers who had there BOV plumed via disconnect into their o/c bailout stage tank and this way going onto your BOV you will not need to take the BOV out of your mouth to go onto your off board bailout tank, keeping your mouthpiece in your mouth to do a easy switch over and yet go off your CCR onto a separate tank at once.
When doing that last switch over to your complete detached and separate gas supply, you as well have decided you are not going back onto the CCR as you have decided you do not trust it anymore, other then providing buoyancy. And you stick with it. And while you at it change your set point to a low one and open the over pressurization valve from your counter lungs as you will go up. The BOV could be a life saver if used properly.
Something else I have witnessed with BOV equipped divers is that they tend not think about what gas they have in their BOV supply tank and use the BOV freely on the surface, and why not. It is that I just always imagine as they go on with their diving career and coming to trimix diving that this habit will have them killed on the surface, due to hypoxia breathing a low o2 content mix on the surface and exerting. As one habit might be good in one diving situation it may kill you in another.
Deep diving with higher pata and with it higher pco2's and a faster need to switch over might warrant the use of a BOV with the added ability of your team mates to help and intervene if you are possibly incapacitated already hy hyper- or hypoxia or hypercapnia..
What I have witnessed over and over again is that divers do hesitate to long, way toooo loooong before they decide to go to bailout ( either o/c SCR or CCR ) when they think something is not right. They start thinking about it, are not sure, they feel something is or was not right, don't want to be embarrassed or think the process of bailing out without a BOV is just to cumbersome and time consuming. The installation and use of a BOV can be a live saver.
If you just think about going off loop and to bailout but can not even put your finger on what or why, that very thought of just thinking about bailout is the very reason to bail out, now. Do not hesitate a split second and go to o/c bailout, because that might have been your last chance to do so.
The installation and use of a BOV can be a live saver. I am diving currently with a BOV (Golem Gear with CCR Megalodon and factory BOV with Classic KISS) and the only exception is my CCR O2ptima who does not have one.
If you have any questions please do not hesitate to e-mail me.