Category — Decompression

Stage cylinders are generally used in addition to “back mount” cylinders or in addition to “side mount” cylinders while cave diving.  The reasons that cave divers, wreck divers and technical divers use stage cylinders include but is not limited to increase the total volume of gas during a dive so that penetration distances or dive times can be greater, to hold different gas mixes (for example a decompression mix, a travel gas, or a bottom mix), to hold a volume of gas needed for team planning or as a safety bottle, and to provide an open circuit bailout source during Rebreather diving applications, to provide safety air volumes needed when planning dives using DPV’s and calculating for failures requiring a swim out.  The diver throughout the entire dive may carry these cylinders, depending on the objective and dive plan, or they may as well be placed along a cave or anchor/ascent line to be retrieved during the exit from the dive depending on the environment and conditions they are diving.

Diving with single and multiple stages in the overhead environment (cave, wreck, or decompression) should only be attempted by divers who have perfected diving skills in their back mount or side mount gear.  These advanced techniques are to be used only once a diver has achieved perfection in the environment they are diving and have a real need and desire to progress greater into the dive.  The reasons divers use stage diving techniques may be enticing but as well with these practices comes a greater responsibility and greater risks for divers to be aware of.  Divers are now entering further into the overhead environment, they may be leaving tanks in water filled caves which may impact the cave, and they are increasing task loading during the dive while making a more complex dive plans.  Divers using the techniques and information in this manual must as well understand and completely accept the risks involved in planning extended penetration dives.

Stage bottles need to be secured to the divers harness via clips to the d-rings. The preferred clip is a bolt clip made out of stainless steel due to a longer life span and ease of use while brass clips become more difficult to operate with time. The size of the clips is depending of the environment, where cold water divers need larger clips due to the gloves or mittens worn. A carry strap can be attached to the stage bottle with the two clips firmly attached to the strap. The strap is used below water to handle the tank and less for the surface. A stainless steel clamp covered in a tubular webbing makes a perfect tank band to hold the strap in place. The connection from tank to clip should be of a cutable kind, a metal to metal connection is not desirable since it can not be cut in case of a clip failure or entanglement scenario when it becomes important to drop or remove the stage tank to solve the problem.

All stage tanks should be labeled clearly in regards to what breathing media is inside the tanks, the marking of maximum operational depth on the side of the tank in large number does have the advantage of the team members being able to see and verify that the correct breathing mixture is being used ant the correct depth.

Each stage regulator does need its own pressure gauge with a preferable short high pressure hose of about 15 cm length. The gauge is bend upward during use and attached to the first stage via a bungee cord or surgical tubing. During periods of non use the gauge can be released to ease the stress on the hose. During the dive when the stage bottle is not in use the valve is to be maintained close, during descent and at maximum depth the valve should be opened shortly to pressurize the first stage, a prevention of water entering the first stage due to pressure differences.

Safety and Deco
Decompression diving and accelerated decompression schedules are in need of a variety of breathing gases ranging from bottom gases to travel gases and a variety of decompression gases. All these breathing media have to be planned, blended, labeled, analyzed and then used at the appropriate time and depth during and according to the dive plan. Depending on the environment dived and the planned bottom times stage tank size and material are of consideration to the diver, while most divers prefer aluminum stages because of their lesser weight and lift requirements.

In ocean drift diving and wreck diving scenarios the decompression stage bottles are usually carried by and with the diver throughout the whole dive, even if that means that the breathing mixture is carried below safe breathing depth. In cave diving scenarios the decompression stage bottles are clipped to the line in a way that not to much stress is exerted onto the line and left at a depth where the breathing gas can be safely breathed, eliminating the potential danger of breathing the wrong mix at the wrong depth.

Extended Penetration
Stage diving must be well thought out. Staging allows the diver to extend the distance of safe exploration. Due to being further into the system it may also produce additional time pressure stress. Training and gradual build up in penetration distances will help offset this stress. In addition stage diving is similar to flying a airplane in that the diver must think well ahead of their position. By thinking ahead and being familiar with stage techniques the diver avoids delays during stage drops and retrievals and the diver will also avoid sudden changes in buoyancy.

Stage and multi-stage diving are other techniques used to further penetration into the caves or wrecks but allows as well longer bottom times during technical dives. When a diver reaches his turnaround pressure but wishes to further penetrate the cave or wreck then a stage or extra tank becomes a necessity. A stage tank can be worn on either side or all on the left hand side depending on configuration preferences. The dive is generally started on the stage tank and when the pre-established turn pressure is reached the diver switches over to another stage or the primary tanks either back mounted or sidemounted. When turn pressure on the primary tanks is reached the diver will turn around and will find his or her stage that was clipped to the line, then change over to the stage tank and exiting the cave or wreck breathing of the stage tank or tanks. Stage diving has a potential high impact on the cave and wreck environment and damage can be extended far into the cave or wreck. Care should be taken not to harm the cave or wreck. Special training is needed to use stage tanks safely in the cave or wreck environment.

Gas and Stage Switching Procedures
How you and your team will switch between your cylinders during the dive needs to be preplanned and practiced in open water situations prior to attempting them in the overhead environment or in real decompression situations.  There are a few common and ¨accepted¨ ways that this can be accomplished.  However your team decides to accomplish gas switches it needs to be remembered that there are many things that can go wrong when switching gases and going to and from regulators.  The end result of an improper switch can end in loss of gas, loss of a way to deliver gas, hypoxic and hyperoxic situations.  Gas switches no matter how done need to have the entire teams attention at 100%.  This is true if you are doing a switch to a bottom gas, travel gas, or a decompression gas.  In addition to verifying your own gas supply and system you must also verify that the other members of your team have made a proper switch as well.

Entire team switching gas and stages
One way that teams prefer to switch gases is the entire team switching at once.  This means that at one point, after the signal has been given and confirmed by the entire team, every member of the team will initiate and switch gases at the same time.  The sequence for this is:

One team member gives signal to switch gases upon arrival at the correct depth or point of dive

1. Team confirms the need and place to switch
2. Every diver locates proper cylinder
3. Divers read labels and check depth vs. MOD
4. Everyone turns on the correct stage cylinder
5. Divers deploy regulator of stage and get it into position to breathe
6. Purge regulator you are planning to breathe from, confirm it will supply gas
7. Switch to new regulator and breathe prior to storing previous gas (you may need to go back to it)
8. Store hose that is no longer needed
9. Trace regulator back from your mouth to the stage bottle and check mix and MOD vs. your actual depth
10. Check other team members to verify they are doing switches and to proper tank and breathing gas
11. Once all team members have switched and confirm okay, continue dive or decompression

This type of switch is best accomplished with all the team members facing each other.  While you are completing each of your steps you are as well going to be keeping up to date with what the rest of the team is doing.  How is their buoyancy, are they at the correct depth, are they switching to the correct tank, is the tank on, is somebody out of gas?  The ability for every member of the team to be able to see each other and the cylinder that each member switches to is critical.  A wrong switch to a wrong tank and breathing gas is a life-threatening event for every member of the team.  Every team member must stay in complete control of the procedures during this time of task loading.

Individual Gas Switches
The second style of gas switching is very similar to the first in the stops but has a different team strategy.  Some teams prefer to switch with one person always acting as observer.  This means that one person will delay their switch and act as an observer until the rest of the team has confirmed their switch.  Upon confirmation of the gas switch of the rest of the team this diver will then switch gases with the rest of the team observing them.  This second way will take a longer time to get the entire team switched but gives you the added benefit of always having one diver less task loaded and paying attention to confirm the switch of the other team members and can respond in case of any failures.

Team member gives signal to switch gases upon arrival at the correct depth or point of dive

1. Rest of team confirms the need and place to switch
2. Rest of team locates proper cylinder (leader does not switch)
3. Team read labels and check depth vs. mod (leader observes)
4. Team turns on the correct stage cylinder (leader observes)
5. Team deploy regulator of stage and get it into position to breath (leader observes)
6. Team purges planned next regulator, confirming it will supply gas (leader observes)
7. Switch to new regulator and breath prior to storing previous gas (leader observes)
8. Store hose that is no longer needed (leader observes)
9. Team traces regulators back to the stage bottle and check mix and mod vs. actual depth (leader observes)
10. Team members verify they are done with switch and to proper tank (leader confirms or makes any adjustments needed)
11. Upon completion and confirmation of the entire teams successful switch the team leader will then start at the top of the list and complete theirs with the rest of the team acting as observers.

While reading this article please keep in mind that 99% of my diving takes place in the caves of the Yucatán Peninsula, Mexico. The opinions expressed in this article are based on my observations of the combined experience of Matt here at Protec, Hans Kaspersetz from Quiet Diver and myself.

Patrick decoing after deep dive in the Pit

I have found the X1 to be an extraordinary tool, considering the environment I dive in and the type of diving I pursue.  The X1’s design and features are both robust and easy to use and facilitate the type of diving I do on a daily basis.

I have used the X1 for: shallow cave diving, teaching and exploring; both in open and closed circuit modes; in environments from huge power passage to tight sidemount cave; for air, Nitrox, Trimix and Heliox; and for up to 7-hour long decompression dives with in water decompression as well as in a habitat.

There are certain aspects that make the X1 the perfect choice for me and here are some of them:

1. The computer is unbelievably small: I think this is a very important factor because of various reasons such as, less entanglement hazard while working with reels and lines, less crowded forearms especially while deep diving and the general minimalist approach of equipment in cave diving. The unit is nicely streamlined and can be carried on both arms with the option of flipping the screen. In cave diving, seize matters!!!
2. The solid body: Anyone that dives in caves will be able to tell you that it is extremely demanding on your equipment. Sharp edges and fine silt that enters even the tiniest orifice put your equipment to the test. The solid body, button less design and wrist mount from Deep Sea Supply combines to make a durable unit that securely attaches to your person.
3. The OLED display: Well, who ever has seen one under water or in pictures knows that the display is very powerful and also readable from almost every angle. A fantastic feature especially for exploring because you can still read the depth reading in extremely low visibility which facilitates the collection of data. In fact the display is so bright that I call it my 3rd back up light.
4. The compass: Honestly I would not use the compass for surveying BUT, you can use it to follow the general trend of the cave while laying line for example. It safes another spot on your arm, two birds one stone.
5. The integrated stopwatch: Very useful for timing decompression stops, low Po2 brakes in the water or habitat, slow final ascents, distances between way points in the cave, runtimes of DPV and many more.
6. The constant updates: Another awesome feature and they are FREE, when you use Ross Hemingway’s V-Planner Live. It is like getting a new computer every couple of months. The new software versions are announced by mail. To download and update your computer takes about 10min and it is easy even for somebody like me who is very inexperienced with computers.
7. The user elected menu list: The new software 4.25 gives you the option to choose the order of the menus. Meaning you can swap things around depending on their importance during the dive. Depending on the type of dive you maybe want to have the compass on first place followed by deco mixes and maybe then the lost gas option or maybe first stop tables then ceilings and display. Before every dive it’s your choice in which order they appear.


Hans preparing for a 325ft / 4.5hours cave dive

8. Plan your dive, dive your plan: I am a fan of Ross´ software since I first used the Z-Planner for deep diving projects in the Egyptian Red Sea. When I got my hands on the first multi-gas computers the calibration nightmare started. I don’t know how often I “bent the computer” because I followed the tables and my computer did not agree…what a nice back up?!? Anyway it always took some time to tweak the settings of the software with the ones of the computer to get them to more or less agree. Now having the same software in the laptop as in the dive computer makes really for nice straight forward dive planning.
9. The use: If this computer was any easier to use a monkey could do it, on a second thought maybe the ones at NASA can. But seriously the menu set up and programming is really great. You still should READ THE OWNERS MANUAL before you use it though. But after sitting and playing with the unit for like 20min you know it inside and out.
10. Customer Service: I have worked in the dive industry for about 8 years and purchased a lot of gear.  Unfortunately, my customer service experiences have been less then satisfying and I rarely have something positive to say about dive equipment manufacturers.   Most will invent the weirdest stories or blame you no matter how something brakes or doesn’t work as advertised. Sometimes it is even insulting.  However, I am happy to report that for the case of the X1 where you have to deal with two manufacturers: Liquivision and HHS Software, I received OUTSTANDING support from Margaret at Liquivision and Ross from HHS. They are incredibly fast when it comes to answering emails, are super professional and very helpful.  I had to deal with them for equipment failures and after a dive accident.

Patrick during Deco

Unfortunately, I cannot report only good things about the X1.  We suffered some hardware failures; however they were dealt with quickly and without cost to us.

1. Problem with depth sensor: There is a known problem, as stated by Liquivision, where the pressure senor port is filled with too much protective white goo.  When the computer is heated up by being in direct sunlight or in the sweltering jungle, the goo expands and the unit senses that it is under pressure and will not turn off.  There are fixes for the problem listed on the Liquivision web site.  If it occurs while on site, Hans discovered that he could just take the computer in the water and the goo shrinks and display the correct numbers.  Liquivision offered to replace the computer.
2. Missing pixels on the display: Matt and I both had some missing lines and missing pixels on the display after only a couple of dives. Liquivision replaced them at 0 cost and we kept the computers (since they were still absolutely usable) until the new units had arrived. The same day after sending a mail to Ross we had a new key to install V-Planner Live again at no cost.

All in all it is really a great tool with a wide range from exploring tiny caves in OC sidemount and getting good readings even in low viz which is crucial for collecting good survey data to several hour long deep cave dives utilizing CCRs with 20 different Bail Out mixes and habitats. The X1 with V-Planner Live is a great product that really jump started a new generation of dive computers. What a great time to be a diver ))

Photos by Matt and Hans