Category — Logistics

To Avoid Breathing Gas Emergencies constant awareness is the key to a successful dive. If a critical situation is developing, react to it before it becomes a threat and call or terminate the dive. Remember the most important rule of diving is that anybody can call the dive at any time, any reason, no questions asked. There are various reasons why a diver could and should abort the dive or even not start the dive at all.

Never dive with minor or mayor equipment problems. Be more conservative on penetration distance on wrecks and caves on turnaround pressure with new equipment, a new cave system or wreck, even new dive partners. Don’t dive with divers who in your opinion do have attitude problems. Always dive within your and your team member’s limits and comfort zone. Do not be “pushed” or push others beyond their self-imposed limits. Allow team members to evolve within their own time and experience frames. In the last years a variety of breathing gases has been used successfully ranging from air to nitrox, trimix or heliox and all divers face the same problem when the tank is empty. Humans cannot breathe water and we are limited to our time underwater depending on the supply of our breathing gas in our tanks.

Running out of gas or air is in most instances operator error and self inflicted. Essential to all successful diving operations is the knowledge of your and your team members breathing gas supply including reserves for emergencies. In recreational non-decompression diving the traditional rule of turn around pressure or return to the surface pressure is 500 – 750 psi / 35 – 50 bar while some prefer to turn the dive at ½ 200 psi / 15 bar to allow a larger reserve. In decompression, wreck penetration or cave diving the rule of thirds is to be observed as a minimum.

Some divers feel that the rule of thirds is not conservative enough and turn at a fourth or sixth of their starting gas volume. Similar Tanks When all divers in a team are using the same size tanks the calculation of the turn around pressure is simple. If a diver has a tank fill of 3000 psi / 210 bar he will divide the initial tank pressure by three coming to 1000 psi / 70 bar for each third. The diver has 1000 psi / 70 bar for the penetration part of the dive, 1000 psi / 70 bar for the exit part of the dive and 1000 psi / 70 bar for a potential emergency. Taking 1000 psi / 70 bar away from our starting 3000 psi / 210 bar we will have a 2000 psi / 140 bar turn around pressure. If a diver has less then 3000 psi / 210 bar, for example 2900 psi / 190 bar then the number will be rounded down for easy calculation, in this case we go to 2700 psi / 180 bar. Dividing 2700 psi / 180 bar by three will give us thirds of 900 psi / 60 bar. Taking 900 psi / 60 bar away from our initial start pressure will give us our turn around pressure of 2000 psi / 120 bar. When ever we have a pressure not easy dividable by three we will round down to find a number easy dividable by three and subtract that number from our initial pressure to find the turn around pressure.

If diving in a team it is important to match the penetration and emergency gas supply by using a simple method. If we have a team of three with same size tanks and pressures for example of 3100 psi / 210 bar, 3000 psi / 200 bar and 2800 psi / 190 bar we look for the smallest number, in this case 2800 psi / 190 bar. We round 2800 psi / 190 bar down to 2700 psi / 180 bar because it is easy dividable by three and coming to 900 psi / 60 bar. Now every diver in the team can use only 900 psi / 60 bar for the penetration and will subtract that number from the initial pressure, arriving at turn pressures of 2200 psi / 150 bar, 2100 psi / 140 bar and 1900 psi / 130 bar. Since all divers in the team are matched and use the same amount of breathing gas to conduct the dive they will have enough gas for potential air emergencies and a safe exit.

Dissimilar Tanks In many diving areas of the world divers own their own tanks with their own volume size and pressure rating preferences. When dissimilar tanks are used we can not use the system of calculating thirds on pressure but must first convert the tank pressure into volume, then calculate thirds on the volume and convert the turn around volume into turnaround pressure. SAC rate Calculation Matching the gas supply is to insure reserve gas supply for emergencies. Gas matching compensates for diver with greatest RMV (Respiratory Minute Volume) or SAC (Surface Air Consumption) to exit sharing gas on smallest gas supply. Carefully estimate distances and gas needs for varying conditions.

The calculation of the SAC rate does begin with measure of gas consumption at a stable depth over a specific period of time noted on a slate for later calculation. Example – 500 psi / 34 bar are consumed in 10 minutes from an 80 cft / 11 liter tank at 100 feet / 30 meter. What is the SAC rate ?. First step is to calculate the minute consumption at depth 500 psi / 34 bar in 10 minutes is 50 psi / 3.4 bar per minute at depth. Second bring depth minute consumption to the surface. We convert the depth of 100 feet / 30 meter into ATA ( Atmosphere Absolute ) resulting in 4 ATA. Dividing our SAC rate of 50 psi / 3.4 bar by 4 ATA will give us the SAC of 12.5 psi / 0.85 bar per minute at the surface. Gas Reserves The rule of thirds is the absolute minimum for technical, cave, ice, wreck penetration and decompression diving due to that fact that the diver has no immediate access to the surface but has to exit the real or virtual overhead environment with a potential problem.

When a diver’s ability to access the surface is limited or non existent he or she must maintain larger gas reserves for potential emergencies. One third of the initial gas supply is used for the penetration part of the dive, the second third is used for the exit part of the dive and at least one third is used and reserved for emergencies. It is that last third that does not belong to us but our team mates that are diving with us in case they are running out of air. It is important that divers monitor their gas volume and pressure gauges in order to return safely from the farthest point of penetration while maintaining sufficient gas volume for exit and emergencies.

Primary gas supplies are managed by a concept called the rule of thirds, which states “ When diving in an overhead environment the unexpected can happen. Since it may be a long way out of a cave it is better to be conservative when applying the rules of gas management ”. The dive must be turned when 1/3rd of the initial gas supply has been consumed. The remaining 2/3rds are then available for use when returning to the exit for any gas related emergencies. The diver should surface with at least 1/3rd of the original gas supply remaining. Good examples of gas-related emergencies are free flowing regulators and ruptured hoses. Manifolds equipped with isolators and dual regulator shut off valves are designed for maximum safety. They allow a diver to shut down a defective regulator and to recover by using the remaining functioning regulator to return to the exit.

It is important to understand that the primary reason for diving the rule of thirds is self-sufficiency. When applying the rule of thirds to dive teams, the number of variables increases. Each diver in the team has his or her own swimming style and normal breathing rate. Moreover, it’s highly probable that team members are using configurations with different tank capacities, sizes and volumes. When this type of scenario develops, it’s imperative that the team matches its gas supplies to insure everyone makes a safe dive with sufficient gas reserves to deal with out of air scenarios.

The first step in gas matching is to insure that the gas has been planned to enable both the diver with the least amount of gas and the diver who has the most gas to exit the cave from the maximum point on the smallest available gas supply. If the dive team has properly matched gas supplies with individual consumption patterns, the rule of thirds provides a secondary advantage. If a problem causes a team member to run out of gas, actions can be taken so all team members can safely exit the overhead environment. For divers to be able to swim as normal as possible in a gas sharing situation, the donor’s alternate regulator should be equipped with a hose at least 7 foot / 2 Meter long hose. The standard 40 inch / 1 meter octopus hose simply isn’t practical when major horizontal distances must be traveled. In addition, a short hose will make it difficult for each diver to maintain contact using a guide line in cave or wreck diving and almost impossible to share air through a restriction.

RMV rate Calculation is the Conversion of SAC into RMV. Imperial – How many cft are 12.5 psi out of a single 80 cft tank. In order to calculate that we need to know what the rated pressure of that tank is, stamped into the neck of each Scuba tank. In case of the 80 cft aluminum tank it is 3000 psi. If we calculate 80 divided by 3000 we arrive at a base line of cft per psi, in this case 0.0266 cft per single psi. For our example above we just need to multiply 0.0266 by 12.5 and will arrive at a RMV 0.33 cft of gas per minute on the surface. Metric – How many liters are 0.85 bar in a single 11 liter tank. The Metric system is somewhat easier to calculate with our Sac rate of 0.85 bar multiplied by the tank size of 11 liter resulting in a RMV of 9.35 liters per minute at the surface.

Live long and prosper. Have plenty of gas to breathe.

Matt

The continuing exploration of particular Cenotes, cave systems and sinkholes within the Yucatan Peninsula takes time in terms of divers committing to exploration with training and experience, the financial as well as the time burden that such explorations are coming with. Another large aspect of cave exploration is finding the right dive team that is equally experienced to dive the cave or sinkhole at hand, to train continuously and work up to the planned dive pluis the logistical support needed for such projects.

decompressing deep diver

In January of 2010 all came together when a polish deep diving team around Jurek and Cezary were ready to continue the deep exploration of the Sabak Ha (Turbid Water) Cenote in the central Yucatan some 60 kilometers / 40 miles south of Merida. I was diving deep in Sabak Ha around 1997 – 2000 to a depth of 150 meters / 500 feet with a large room clearly continuing horizontally as well as vertically down. No walls where to be seen, no ceiling and no bottom with a visibility of around 30 meters / 100 feet. When Jurek heard about this site we went for a recon dive earlier this year ,and he was all for a project to push the boundaries.

lowering gear to the water

The 2010 exploration team consisted of Jurek and Cezary as deep push divers, Robert and Dariusz as support divers, Conrad filming underwater, Jacek and Piotr filming on the surface. me from the ProTec Dive Center in Playa del Carmen was responsible for local support, logistics, gas mixing, photography underwater and on the surface, liaison with local authorities and press as well as translation. All participating divers where technical cave divers as well as Trimix divers experienced in deep cave diving as well as Mexican cave diving. Dive team preparations prior arriving in Mexico included multiple deep cave diving in the Red Sea in the 100 – 120 meter / 330 – 400 feet range to get the team procedures in sync. When the dive team arrived in Q. Roo during the beginning of January 2010 three days of horizontal cave diving in large doubles where conducted to acclimatize to Mexican caves and the tanks to be used during the deep diving project.

For the first deep diving day in Sabak Ha all breathing gases such as a number of Trimix mixtures, Nitrox and oxygen were mixed by me in Playa del Carmen’s ProTec Dive Center. A total of 25 80 cft alm stage tanks, 2 sets of 80 cft alm double tanks, 2 sets of 104 cft steel double tanks and 2 sets of 125 cft steel doubles tanks got filled, rigged and came along for the trip. This was going to be an all open circuit assault as all divers where experienced in open circuit deep diving. The project was scheduled in a way to dive one day then mix gases / rest the next day, dive one day then mix gases / rest the next day, and so on.

mixing it up

After arriving on site at the first diving day all came together as we met our porter team around Dionicio and Chepo from the Ecology Department of Yucatan who introduced us to the helping hands they had organized. The 2010 Sabak Ha exploration project was in the planning for over 6 month with continuous support from the Ecology Department of Yucatan who contributed with a rescue team and vehicle on site. As all gases where mixed in Playa del Carmen the team went to the dive site for a recon dive that led the whole team to a depth of 65 meters / 215 feet. During that time one camera man was diving with the team documenting the environment, two camera men stayed on the surface documenting the surface activity and I me remaining on the surface organizing the surface support as well as taking still images for later articles that where to be published in Poland.

gear assembly

underwater camera man

The next day after the recon dive was a mixing day with a 6 hour long mixing session at Dutton’s Machine Shop in Merida, the only filling station in Merida. During that mixing session a number of breathing mixes did not turn out the way they should have been. The affected breathing mixtures were analyzed and identified the same evening but could not be changed due to fill station time restraints and gas supply company hiccups, the gas company not being able to deliver the gases I had reserved and they had confirmed. The blending issue was identified to as helium tanks containing less than 100% helium. The average helium purity was established and analyzed around 93-94% helium, with one tank 70% helium and another 80% helium. This mix up of breathing gases could have been easily avoided if I would have analyzed all helium tanks for helium content before starting the mixing process. In order to fix the breathing mixtures the next planned diving day fell into the water as the remixing of a number of Trimix mixtures took some 3 1/2 hours as soon as the filling station opened, and at this time the dive team did not feel it wanted to be rushed into deep cave diving, and canceled the dive of this day.

fill station in Merida

The second diving day lead the deep diving team to the 100 – 110 meter / 330 – 360 feet horizontal passage from where the line leads into the large room where no walls, bottom or ceiling can be seen. When continuing into this passage exploration starts at 120 meters / 400 feet horizontally and when following the line down at 150 meters / 500 feet depth at the end of the line with no bottom in sight. The deep team was continuously documenting the whole dive with a helmet mounted video camera. The shallow diving team went into the shallower 65 meter / 215 feet cave passage to investigate the potential for further exploration. During that dive the underwater camera man was filming the deep team to a depth of 100 meters / 330 feet while this author was taking underwater still images to a depth of 30 meters / 100 feet as well as surface photography.

Due to delays with the gas company providing the helium and oxygen, and the weekend becoming a major factor of not being able to blend breathing gases in the fill station the day was used to shoot surface footage at the Uxmal ruins. Nice day, nice footage, not much diving through. At this time the project schedule started to slide but the day in the ruins was a great way to not think about diving too much.

The following day started with fully restocked helium and oxygen supplies and the next 6 1/2 hour mixing marathon session began to blend breathing gases for the upcoming push dive. This time we had no bad helium tanks but all tanks were analyzed to be around 93 – 94% helium. While being at the fill station all day long I really appreciate the help from Elias who helped me so much pumping all that air that was needed to drive the so important booster pump as well as to top of all them tanks.

tanks come up the line in darkness

The next diving day came with us leaving Merida around 8:00 am from the Tecnotel Motel right in Merida and close to the fill station with about an hour’s drive to the village of Mucuyche where we met at the house of Dionicio and Adelaida to gather the rest of our porters. Today old trusted Pedro came along to help out, bringing the porter crew up to four porters. Arriving shortly after 9:00 am at the dive site it took about 1 1/2 hours to get all the tanks set up, down the rope and towards the water’s edge. The rescue teams daily arrival was around 11:00 am, just before the divers went into the water. The hang line was installed daily to hang travel gases, deco gases and extra tanks onto the line prior the divers went into the water. Support divers verified the tank depth. During the deep part of the dive one of the deep support divers got entangled into the guideline at around 100 meters / 330 feet depth and the guideline had to be cut to free the support diver. At this moment the dive was called and the divers came back to the surface well before the 6 hour long planned dive that would have been the push dive. Better safe than sorry.

tanks come up the line in darkness

As the project time was running out slowly with the project duration coming to an end it was decided to do one more dive to fix and repair the guide line at 110 meters / 360 feet in order to leave an continuous guideline for following dive teams. Breathing gases where filled and remixed early in the morning the same day with a late start arriving at the dive site at 11:00 am putting the divers into the water around 13:00 pm. The deep diving team was able to repair the line on this last dive and to push on into the deep part of the cave to a depth of 130 meters / 430 feet. As we had a late start into the dive darkness came up fast. The generator was started up around 17:00 pm providing light with two 500 watt working lights, thus enabling the surface crew to safely bring all the tanks back up the line and stored into the vehicles.

During our stay we gave a number of interviews for local news papers and local TV stations that demonstrated that the local populations interest in how the sinkhole of Sabak Ha, the deepest geological feature of the Yucatan may continue and what new passages might be found. During the diving days we had quite a large number of up to 40 visitors that came from the surrounding villages to see what we do, have a chat and lend a hand.

As the project came to an end the team did no reached the goal they came here to Sabak Ha to fulfill, the exploration to maximum depth, however, the team established the potential of exploration at the 120 meter / 400 feet plateau. When the guideline broke it became a priority to repair the guide line and they spend a dive on repair instead of a deep push dive. During the four conducted deep dives no one was hurt, no one was bent, not even a strained ankle, shoulder or scratch on the arm. As it turns out at times deep cave exploration is not an easy feat but if you can walk away from it and talk about it, it was a great successful project. The dive profiles where for dive 1) to 60 meters / 200 feet, 20 minutes bottom time, 1,5 hrs total time, dive 2) to 60 meters / 200 feet dive, 30 minutes bottom time, 2,5 hrs total time, dive 3) to 113 meters / 370 feet, 17 minutes bottom, 2 hrs 15 minutes total time, dive 4) to 100 meters / 330 feet, 11 minutes bottom, 1,5 hrs total, dive 5) to 130 meters / 430 feet, 30 minutes bottom, 4,5 hrs total time.

decompressing deep diving team

I would like to thank the Ecology Department of Yucatan for their support, the Bomberos rescue team to be there for us, the porter crew to make it happen, Adelaida for the great Yucatecan food, Pedro to not give up teaching me some Maya and Dionicio to have the great skill to move a mountain of equipment without a scratch.

I would like to thank the Polish deep team Jurek and Cezary, the support team Robert and Dariusz, the underwater camera man Conrad, the surface film crew Jacek and Piotr to come here to Mexico and trying to push the known boundaries of these deep caves. I would like to mention as well that part of making the project happen was the generous project support of the main sponsor Infovide-Matrix a Polish IT consulting company which also sponsored Jurek’s 231 meter / 757 feet depth record in 2007, the main media patron National Geographic Poland and the equipment sponsored by Liquivision – X1 Trimix computers and Ammonite Polish underwater lights.

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