Category — Bailout

When diving into caves, wrecks or under ice divers are introduced to a number of hazards not associated with open water diving. Some of these are easily managed. Others may be life threatening. General hazards include total darkness, loss of visibility, increased potential for confusion, unexpected currents, cave ins, restrictions, depths, unknown distances, mazes, turbidity / silting, current, sharp surfaces and projections, collapse, debris slides, restrictions minor and major, depth, distance, time.

Darkness

Absolutely no light penetrates most cave systems and one of the first things to realize is that the darkness is total. Not the slightest bit of light penetrates the solid rock ceiling, there are no stars and there is no moon. In caves the prospect of being lost in the dark can have chilling effects. When lost or when loosing ones light stress levels typically climb. Don’t let panic skyrocket. Cave diving requires disciplined self control to function correctly. This discipline must be learned and practiced.

Being Lost

Several common factors, or combinations of factors, contribute to the possibility of a cave diver becoming lost. Becoming lost is a threat on any cave dive. Caves frequently present divers with a number of mazes, dead ends and multiple levels of formation. Accidentally wandering into an unintended passageway can result in dive partners becoming lost. In fact, one of the leading causes of cave fatalities is the failure to follow a continuous guide line and set jump lines that lead all the way back to the surface. Guide lines are the diver’s path back to the entrance, they are a cave divers life line. Guide lines offer life insurance by providing cave divers with a marked path to the surface. It is imperative to keep an eye on these lines at all times. When visibility is good you should swim close to the line at all times so the line can be easily located. It is important not to stray too close to the line neither since the possibility of becoming entangled in it increases. Entanglements can become killers because they can result in broken or loosened lines. When limited visibility conditions occur, one must stay closer to the line. The best technique to stay in touch with the line once visibility has deteriorated is to swim with your thumb and forefinger forming a ring and looped over the line.

Visibility

In explored caves it is common to find permanent lines with arrows pointing toward the nearest route to the surface. Turbidity is caused by stirring up debris on the cave floor due to poor swimming techniques or due to percolation when exhaust bubbles hit the ceiling. It can reduce visibility to zero within seconds. From both a dive safety standpoint and an environmental point of view with cave conservation in mind, it is important for you not to stir up the bottom of a cave. Tannic acid is the color of soil and can be washed into the water by rivers or rain. It has the color of tea or coffee with the same visibility characteristics. A Halocline is the interface of fresh and salt water and when mixed produces zero visibility.

Water Flow

Current in caves can range from none to mild and even to severe. New cave divers are often intimidated by these currents. They tend to overwork and become tired quickly. By carefully employing proven techniques, the work may be reduced to a less demanding level. The best way to beat the current comes with learning to read the cave. Areas where the surface is smooth have been polished by the flowing water. So, you should look for jagged and pitted surfaces. They exist where the current is weakest. Current can also be out flowing or in flowing. Sometimes caves divers may encounter passageways featuring flows differing in direction from the passage currently being explored.

Cave or Wreck Collapse

Cave-ins ( collapses ) are rarely encountered in cave diving. Water pressure acts as a support and stabilizes submerged tunnels. It is only when water levels drop that the possibility of collapse exists. Occasionally, in some caves a small portion of the cave structure will fall in.

Debris

During floods, debris builds up in the down slopes of cave openings and in the runs. When the water table drops, additional debris is blown out of various passageways and is deposited on the cave floor. As these strictures extend toward the surface, more debris builds up in the run. At some point, the volume of these deposits reaches a point where gravity causes it to slide back into the cave. The result, in both cases, is an instantaneous loss of visibility. In fact, on one of these occasions visibility can be so obscured that it would proof impossible to get out if divers hadn’t had the mandatory foresight to install guide lines beginning at the cave opening. In some situations, it is possible that the cave opening actually becomes blocked.

Restrictions

Restrictions are choke points where access is reduced. They can be either minor or major. A minor restriction is a slight narrowing which, although restricted, still allows two divers to pass through it not side by side or on top of each other but in a single file following one another. A major restriction, on the other hand, only allows one diver to pass if the equipment is to be taken off and pushed through the restriction. As a rule of thumb the equipment is never taken off due to potential problems with buoyancy, damage, entanglement and cave conservation. If the need arises to pass through a mayor restriction gear configuration such as sidemount or no-mount have to be implemented. Obviously, the risk associated with a major restriction involves becoming stuck. When entering restricted areas be careful to evaluate the best passage route while also concentrating on relaxed breathing. If stuck, exhale some air and slowly maneuver your body and simply dislodge your self. Do not try to “ power through ” restrictions. You may become severely wedged. We can’t stress it hard enough. Take it very easy when swimming in tight spots. It is very easy to tear a BC bladder or damage your gear. Again, learn to read the cave and avoid abrasive and protruding surfaces.

Depth

Depth in caves can be very deceptive because you have a roof over your head and a floor under your feet. Don’t forget to monitor depth regularly. Depth increases gas consumption, the risk of nitrogen narcosis arises, can cause oxygen toxicity and produces a greater decompression obligation. This is why many cave divers use Normoxic or Hypoxic Trimix mixtures for deep cave exploration.

Distance

When a problem arises we realize it’s a long way back. Distance, in this instance, may produce additional time-pressure stress. In worst case scenarios, your gas supply may be compromised if one team member experiences gas failure. Training and awareness, combined with careful planning, will enable you to deal with the hazard of distance. The ceiling over your head prevents direct access to the surface. This is why highly reliable equipment combined with redundancy is used for cave diving.

Changes in respiratory patterns, such as response to mental and physical stress will also increase gas consumption. When divers slow their pace, gas consumption is reduced. Never forget that your exit speed must match your entrance pace. You must cover the same amount of ground in the same time “coming out” as “going in” to insure you won’t run out of gas.

Air and Team Management

Since dive teams are obviously composed of individuals, a “ team gas management ” rule must be established. This rule incorporates all the factors involving individual considerations with another dimension. This dimension is created by people working together. When diving alone, dive techniques and gas management are different as if diving as a team member of a dive team.

The size of the dive team will dictate effective gas management. Obviously a two person dive team is the most efficient from a dive performance standpoint. It needs less communication and requires less choreography. Both divers know where their partner is. Swim pace is easier to regulate. A small team reduces the level of environmental management needed. For example, silting is just one of many factors that’s easier to anticipate and prevent.

However, there are strong arguments to support the advantages of a three person dive team. The group gas supply can go much further when shared between three people. Two people are usually better able to rescue an individual in trouble. Irregardless, the gas plan to be used must be developed from a swimming based surface rate ( vs. a resting rate ). It must be fine tuned by adjusting anticipated gas consumption against the environmental factors you expect to encounter. Experience has taught us this method is almost always totally accurate for planning dives involving a lot of swimming. To do this right, all dive team members must know their individual RMV’s.

Even with proper gas matching, it is still imperative that all dives remain within normal parameters for these rules to work. When conducting cave diving on your own, or with new team members, it is advisable to add a couple of hundred psig / dozen bars to any turn around point and turn around earlier. This practice should be continued until divers have sufficient experience to develop the discipline to function normally under stress.

Running out of Air

By taking corrective actions with gas supply problems, for example, before things escalate, divers can begin sharing gas before the diver with the problem actually runs out completely. This is good stress management. It allows the distressed diver to use his or her own gas whenever a restricted or hazardous point in the dive is reached and share air in the long, unobstructed passages. Once any member of the dive team is using a back up regulator, the dive should be terminated. All divers should begin their pre-planned exits.

Die Meisten von euch werden jetzt wahrscheinlich denken, dass ich etwas über die tiefen Höhlen in Yucatan, über The PIT oder vielleicht The Blue Abyss schreibe. Aber Kreislaufgeräte sind nicht nur für das Tieftauchen geeignet sondern durchaus auch für die relative flachen Höhlen hier in der Riviera Maya.

Generell taucht man in die Höhle bis ein drittel des Gas Volumens verbraucht ist und dreht dann um. Wenn man bedenkt, dass viele Höhlensysteme hier mehrere Kilometer lang sind kann es einige Zeit dauern bis man ein System besser kennt. Die Höhlen hier sind wie ein Schweizer Käse mit vielen verschiedenen Gängen und Tunneln. Wenn man einen guten Überblick bekommen will hat man “offen” nur ein paar verschiedene Möglichkeiten, entweder macht man mehrer Tauchgänge, verwendet einen Scooter oder berechnet die drittel Regel neu für jeden Seitenarm der Höhle. Egal für was man sich entscheidet, wenn man “offen” taucht läuft die Zeit gegen einen. Oft kommt man zu einem traumhaft dekorierten Raum und hat keine Zeit ihn zu bewundern da man zum Umdrehen gezwungen wird.

Howard mit seinem Optima in der Grand Cenote

Der Vorteil des Kreislaufgerätes ist dabei, dass, so lange man innerhalb seines Bail Out Radius bleibt, man von Leine zu Leine springen kann wie es einem gefällt. Der Bail Out Radius wird dabei vom Gasverbrauch und Bail Out Gas Menge bestimmt.

Angenommen die Höhle ist maximal 12m tief und der Taucher hat einen Gasverbrauch von 20 Litern die Minute ist sein Bail Out Radius ca 50min. Oder man kann auch die Distanz verwenden. Der Taucher schwimmt in seiner Ausrüstung ca. 15m pro Minute also darf er nie weiter von einem Ausgang entfernt sein als 750m. Alle Werte kann man individuell auf jeden Taucher und jeden Tauchgang abstimmen und gegebenenfalls Konservativer sein. Taucht man im Team bestimmt der Taucher mit den höchsten Werten die Grenzen des Tauchgangs.

Taucher mit Kreislaufgerät in Nohoch

Auch wenn man zum Beispiel in einem Teil der Höhle mehr Zeit verbringen will um zu Fotografieren oder einfach nur die Formationen zu bewundern hat man durch das Kreislaufgerät die Möglichkeit dies zu tun ohne jemals Zeitdruck zu verspühren.

Ich bin gerade dabei einen Rebreather Taucher hier in den Höhlen zu führen und stelle jeden Tag aufs Neue fest welche tollen Möglichkeiten man hat.

Am ersten Tag waren wir in Ponderosa und sind dort Stromaufwärts getaucht. Unser Bail Out Radius war 40min, also sind wir einfach dem Hauptseil entlang getaucht und haben nach 40min umgedreht. Anstatt dann aber zurück zum Ausgang zu tauchen so wie wir das tun würden wenn wir offen unterwegs wären, haben wir zuerst den Sprung nach rechts am Orangen Pfeil gemacht. Sind diesem Seil gefolgt bis zum T am T nach links dann wieder umgedreht zurück zum T dann T nach rechts da wieder umgedreht zurück zum Hauptseil dann den Sprung nach rechts bis zum T und so weiter und so weiter. Durch die Kreislaufgeräte hatten wir eben die Möglichkeit uns so gut wie ALLE verschiedenen Seile dieser Region an zu schauen und dabei aber immer noch die Zeit haben mal wo länger zu bleiben für Fotos oder einfach nur zum staunen.

Am nächsten Tag ging’s nach Taj Maha wo wir zuerst dem Grottenseil gefolgt sind und nachher den Sprung gerade aus gemacht haben Richtung Chinese Garden. Wir sind hoch bis zum “Wasserfall” getaucht, haben uns dann den Loop angeschaut, dann weiter zu Steves Loft dann runter Chinese Garden zurück zum Sprung und dann nach rechts und den alternativen Tunnel hoch. Ein traumhafter Tauchgang indem wir uns jede einzelne Leine dieser Region angeschaut haben.

Patrick mit dem KISS Rebreather

Am Samstag waren wir dann in Nohoch Nah Chich dass mit seiner maximalen Tiefe von 6m uns einen fast endlosen Bail Out Radius ermöglicht hat. Der Spielplan war wieder der Gleiche, ein Seil entlang tauchen bis zum Umkehrpunkt und dann beim raustauchen alle Möglichen Sprünge nach rechts und links machen. Ich habe somit viel besser die Möglichkeit mehrer Highlights in nur einem Tauchgang zu bestaunen anstatt mich immer für etwas entscheiden zu müssen.

Sonntag haben wir pausiert und heute waren wir in der Grand Cenote nahe Tulum. Auch hier haben wir was ich normalerweise in 3 bis 4 Tauchgängen machen würde in einem gemacht. Wir sahen die ganze Cuza Nah Schleife inklusive dem Sprung in der Mitte dem wir gefolgt sind bis es für die Rebreather zu eng wird tauchten hoch zu Paso de Largato und Much’s Maze, die Abkürzung am Hauptseil und so weiter.

Morgen geht’s ab nach Aktun Ha was auch als Carwash bekannt ist. Ich freu mich schon sehr darauf den Bail Out Radius von Luke’s Hope neu zu berechnen und dann super viel Zeit im Room of Tears zu verbringen und hinten die ganzen Ts ab zu tauchen.

Howard mit einem Dive Rite Optima

Natürlich kommt das alles nicht ohne ein paar Nachteile. Wie alle Rebreather Taucher wissen ist es nicht so einfach eine gute Tarierung mit dem Kreislaufgerät zu haben und wenn man nur Zentimeter über einem mit feinen Sedimenten uebersäten Boden schwebt, kann das schon schwierig werden. Weiters sind die meisten Kreislaufgeräte durch die umgedrehten Flaschen relative schwer an der Hüfte was sich sehr stark auf die Position im Wasser auswirkt. Mit anderen Worten ist es schwieriger mit dem Körper horizontal, parallel zum Boden, zu tauchen.

Auch an das Sägezahnprofil der meisten Höhlen hier muss man sich erst mal gewöhnen.

Alles in allem bin ich aber der Meinung dass man mit einem Kreislaufgerät hier in der Riviera Maya auf jeden Fall auch in den flachen Höhlen tolle Möglichkeiten hat und zusammen mit den tieferen Höhlen auf jeden Fall das volle Potenzial dieser Maschinen ausnutzen kann.

Keep your mind open

And your loop closed

Patrick

A Bail Out Valve (BOV) is a Diver Surface Valve (DSV) that has a second stage regulator incorporated into the mouthpiece and is connected to either the onboard diluent tank or the off board bailout tank thus supplying the diver with open circuit breathing gas. A rebreather diver who is using a BOV is either on the loop breathing of his rebreather or on the regulator breathing open circuit enabling him to have a breathing source at all times.

There is a variety of BOV’s on the market now, some rebreathers are coming factory equipped and stock with a BOV while others can be fitted with aftermarket BOV’s. Most BOV’s have a drum within the mouth piece and when turned allowing breathing gas upon inhalation either be taken in from the rebreather or the open circuit regulator. Some BOV’s are very sophisticated with magnetic switches inside actually allowing the electronics to see if the diver is on the loop or on open circuit.

BOV fitted onto Megalodon loop

Why or why not to use a BOV seems to be a personal preference until you look a little deeper into it. Of course the opinion expressed here is my personal one but has developed through time while witnessing first hand events that could have been handled better with a BOV or hearing from other divers what happened to them. 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 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 is just to cumbersome and time consuming. The installation and use of a BOV does change that and can be a life saver.  

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 very high Pco2, experiencing extreme hypercapnia. The dive partner realized what is going on and urged the his friend 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 back up to the surface and both lived to tell the story. With a BOV the diver would have been able to switch from his rebreather to his o/c bail out without a problem and without the need to take his mouthpiece out of his mouth. Additionally the other diver could have intervened and help the affected diver while turning a simple knob on his friends BOV mouthpiece, helping the distressed and potentially incapacitated diver.  

Something else I have witnessed with BOV equipped divers is that they tend not to think much 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 somewhat uncomfortably 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 potentially hypoxia breathing a low o2 content hypoxic breathing mixture on the surface, possibly exerting while moving along the surface toward a down line or trying to catch up with a boat or drift line. As one habit might be good in one diving situation it may kill you in another.

Shall I connect the BOV to my inboard diluent tank or to my off board bailout tank. Well, that depends on the depth you want to dive at as usually your inboard diluent tank is rather small unless changed to a larger tank to allow such move. My thought is a bit deeper though. I believe that if I decide to go off my rebreather (SCR or CCR) then I am off and want to go to something that is not connected at all to my rebreather because my rebreather is my rebreather and my bailout is my bailout, separated entirely and not connected to one another. Personally my BOV is connected to the inboard diluent tank.

two Megalodon divers fitted with BOV

When doing that last switch over to your complete detached and separate bailout gas supply, you as well have decided you are not going back onto the rebreather as you have decided you do not trust it anymore, or it does not work anymore other then providing buoyancy. And you stick with it. And while you are at it change your set point to a low one or manual, open the over pressurization valve from your counter lungs as you will go up and if using electronics or dive computers with ccr - o/c capability do the witch there too. The BOV could be a life saver if used properly.

BOV on KISS diver

I have seen some divers who had their 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 rebreather onto a separate tank at once. That is fine if that is what you want to do but as I am feeling strongly about team diving I would still need to have a second stage regulator connected to my bailout tank in case my team mate is in need of bailout gas.

BOV on P-SCR diver

With the limited volume offered by the onboard diluent tank the BOV is just an important step in-between to get off the loop and then onto the separate bailout tank (I will discuss other than o/c bailout options in a future post). While taking a breath or three while on my BOV connected to my inboard diluent tank I have time and a controlled breathing gas while looking for my main bailout tank regulator, then go on to my large o/c bailout stage, which is a completely separate life support system with pre-calculated Po2 and gas volume.  

If you just think about going off the loop and to bailout but cannot even put your finger on what or why, that very thought of just thinking about bailing out 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 currently have a BOV on almost all my rebreathers using a Golem Gear BOV on my CCR Megalodon and Inspiration, and manufacturer BOV with Classic KISS as well as P-SCR. The only exception being my CCR O2ptima who does not have a BOV, but I am sure thinking about installing one. In deep diving with higher Pata and with it higher Pco2’s or in cave diving when dealing with navigation in case of a breaking through, the fast need to switch over to bailout might warrant the use of a BOV with the added ability of your team mates to help and intervene if you are possibly incapacitated by hyperoxia, hypoxia or hypercapnia.

Matt