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Cave Diving &CCR Training

Cave Diving &CCR Training

tech talk What to do when things go pear- shaped...

Edited by Michael Menduno & CCR Training

Text and photos —The Issue of Bailout Gas courtesy of

Remember the first rule to all technical divers without Here’s one reason why. On journey might be fine as long as of that exception. a , the exhaled gas ’s CCR continued to Given all that, what’s diffi- is recycled and the carbon function as it should. But what if you were taught in your cult to understand, is why some dioxide is removed by a little it did not? basic open-water class? I folks seem to lose the plot when chemistry set carried in the unit’s believe it goes something they strap on a rebreather… scrubber. Apart from a few litres Sense-check like: “Keep !” even more baffling is when they of diluent gas used up now and OK, sense-check time. I strap on a rebreather and then again, all the gas that needs have more than a few Simple advice and unar- swim into a cave while seem- to be added regularly to “the dives in on a guably the best advice ing to ignore the primary direc- loop” (the going rebreather and have possible for any diver, not tive… always have something to round and round in the unit) is yet to have my unit just those entering the breathe. the metabolized by the fail on me. I have run You may already know about diver as she swims. A working out of diluent during sport for the first time. , and you may also average for this is about 1.5 litres a dive—operator be a cave diver. But for those of per minute, and this does not error because I For example, the same first rule you who are only one or the oth- significantly change with depth. was playing silly is true for . Gas er—or neither—here is the Coles In other words, a three-litre bot- buggers—and management 101 starts off by Notes version of your CCR cave tle charged to 200 bar with I have had stating something like: “Always class. A rebreather offers divers oxygen can last for up to 400 a couple of have a sufficient volume of the ability to get a long, long minutes. incidents that appropriate gas to breathe way from fresh air without much What that means is that if we required me throughout the whole dive!” effort. Unlike an open-circuit were to say that the average to take the More wordy—and there are cave diver who generally has cave diver on an easy outing initiative and other nuances to a gas plan to carry many stage bottles of swims at a speed of between 15 fix some- such as having gas to share with gas to extend her foray into the to 20 meters a minute, that vol- thing on your buddy—but the message to deepest regions of a cave, way ume of oxygen could translate the fly—op- the tech crowd is essentially the back from the exit, a CCR diver into more than 6,000 metres of erator error same as it is to the new diver. can push many hundreds even distance round-trip! or inten- And unless I’ve missed a memo thousands of meters without Now here’s the problem. tional skills somehow, that message applies making any allowances at all. Everything on that six kilo-meter testing—but

81 X-RAY MAG : 55 : 2013 EDITORIAL FEATURES TRAVEL NEWS WRECKS EQUIPMENT BOOKS SCIENCE & ECOLOGY TECH EDUCATION PROFILES PHOTO & VIDEO PORTFOLIO alexander lucas / wikipedia commons with an AP tech talk rebreather Bailout

the truth is that I have not had to bailout let’s call it “sufficient volume bailout” for in earnest in a cave while diving a CCR. the time-being. Put it down to luck or using a before every dive, but my CCR cave Dive buddies dives have gone remarkably smoothly… When things go pear-shaped under- thus far. I have probably jinxed myself water and stuff hits the fan, the simple now. are generally the most effec- tive and safest. On occasion a Bailout involves or requires the help of a dive Beginning CCR divers doing entry-level buddy. Technical diving is a team-ori- CCR programs are often taught that if ented sport and when things go wrong anything goes wrong with their unit, they on a technical dive—and everything is should bailout. In other words, switch to aligned perfectly—we have one or two open-circuit and get the heck back to buddies to help out. All this aside, we the surface and sort things out there. are also taught that a diver should be One might argue that with all the vari- capable of finishing her dive on her own ous options that a rebreather gives its and that the safest team is built around operator, bailing out is not always the individual members who are perfectly best option, and teaching users to react capable of self-rescue should the need this way as a default does not take full arise. This becomes particularly true in an advantage of a CCR’s strong points. But overhead environment, and in the vast for the sake of brevity here, let’s assume majority of cases, self-rescue (perhaps that bailing out to an independent open- under the watchful eye of a companion circuit gas is “best-practice” for a cave ready to help out if needed), is the sim- diver with a problem. It follows then that plest, most effective and safest solution in to be ready for a dive where things fall a cave. off the rails, a CCR cave diver needs While it’s fine to believe in the tooth to carry some bailout gas so that she fairy, Santa and the Easter bunny, my always has a sufficient volume of appro- advice is to be very skeptical that the priate gas to breathe throughout the gas pixie will show up when you are in best practice would seem to be for every SAC to RMV tor to account for the workload, etc, for whole dive. So far so good. desperate need of a lung-full of some- CCR cave diver to carry enough gas The process of converting a personal the dive. I have heard CCR divers talk about thing nice to breathe—especially in a to get themselves out solo. It would be SAC rate (Surface Air Consumption) to Here’s a simple example. Let’s use a a technique called “Buddy Bailout” or cave. Even though we teach air-sharing nice to think that when a CCR diver is a RMV (Required Minute Volume) is as SAC of 15 litres per minute and a cave “Team Bailout”. This essentially means in open-circuit cave programs, there an hour’s swim from the cave’s exit, and straightforward in CCR cave diving as it is dive on which the average depth is 25 that each diver does not bother to carry is little in the skill as practiced by most they discover that they have no option in open-water open-circuit diving… with metres. Let’s also say this cave is familiar the gas he or she would need to swim divers that will help out in a real OOA but to bailout, that their dive buddy is one added step. to the diver, has light (out-flow) out of the cave from the furthest pen- event fuelled by and desperation. within arm’s reach and not swimming SAC (the volume of gas a diver and the water is relatively warm and etration point to the exit. They would per- Added to this, and informed by experi- away blissfully unaware of the problem. breathes each minute) is a constant and clear (21 degrees and more than 30 haps carry half of the volume required, ence, is a pretty solid opinion that opera- It’s wonderful to have a buddy’s gas as is influenced during a dive by several metres of vis). For this dive, we might use and will “get the rest” from their buddy. I tions such as handing a bottle off to a a backup, but primacy dictates that you other factors such as depth, workload, a dive factor of 1.50. am not sure how you feel about this, but companion, while in a small passage have sufficient gas to exit without their stressors such as water and So here’s the arithmetic: 15 X 3.5 (25 it gives me the willies. with silt for a floor, and with one of the help if possible. Which brings us to a word visibility. The simple conversion for SAC metres expressed in absolute ) X Here’s an outline of another technique, party fighting for air, will not end . about how to calculate how much gas is to RMV is to multiply SAC by depth, and 1.50. The result is an RMV of approximate- which doesn’t have an official name, but Taking all this into consideration, the enough. then multiply that number by a dive fac- ly 80 litres per minute (78.75 l/m).

82 X-RAY MAG : 55 : 2013 EDITORIAL FEATURES TRAVEL NEWS WRECKS EQUIPMENT BOOKS SCIENCE & ECOLOGY TECH EDUCATION PROFILES PHOTO & VIDEO PORTFOLIO tech talk

join the rebreather revolution

ABOVE The author using his AP rebreather at Jackson Blue Springs, , USA

So far so good. If we are planning these events could be carbon diox- If the first rule of technical diving is: a dive to swim into the cave for 40 ide break-through, and this might “Always have a sufficient volume of Poseidon MkVI minutes before we turn, we will need influence the rate of the appropriate gas to breathe through- The world’s first fully automatic, approximately 40 minutes-worth of diver… dramatically, and for several out the whole dive!” then perhaps recreational rebreather gas if our unit fails us at maximum minutes. In other words, the 3,200 the first rule of CCR cave diving penetration. That equals 3200 litres… litres that we calculated to get a should be: “Never take a CCR into a Now available at or a 16 litre cylinder pumped to 200 diver from maximum penetration cave that you have not swum out of Poseidon Rebreather Centers worldwide. Visit poseidon.com bar… or one and a half 11 litre tanks to the surface might not be quite using open-circuit.” for your nearest center and filled to 200 bar. enough. We might need to revisit the Final word: take notes… read them for further information on Now this assumes something Dive Factor and change it from 1.5 to often! ■ the Rebreather Revolution. critical, and something that is dif- an even greater number. ferent for a CCR diver compared Of course, back-of-a-napkin calcu- Steve Lewis regards himself as a cave to an open-circuit diver. The criti- lations such as these are fine discus- diver, primarily. He is a technical cal difference—the additional step sion points while chatting with friends instructor-trainer with ratings from TDI that separates this type of calcula- someplace warm and dry with a and PSAI, and among other foibles, tion for a CCR diver as opposed to plate of olives and a glass of wine on teaches divers to have fun and stay an open-circuit diver—is hidden in the table in front of you. However, safe on two very different CCR units, the nature of the possible events the only truly safe numbers come neither of which lends itself, in his www.poseidon.com that would cause a CCR diver to from what is euphemistically called opinion, to team bailout. bailout in earnest and completely “field-tested data”. And these you from her rebreather’s loop. One of need to collect yourself.

83 X-RAY MAG : 55 : 2013 EDITORIAL FEATURES TRAVEL NEWS WRECKS EQUIPMENT BOOKS SCIENCE & ECOLOGY TECH EDUCATION PROFILES PHOTO & VIDEO PORTFOLIO

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