My humbling experience with a Closed-Circuit Rebreather Course

After 15 years of diving the beautiful reefs in S.E. Asia, I decided to try something different. One with a higher element of thrills and that will challenge me both physically and mentally. A TDI closed-circuit rebreather course. With so many rebreathers endorsed by TDI e.g. Inspiration, Evolution, KISS, Megalodon, Pelagian, Poseidon Discovery and more, the question is which one to choose?

I had heard and read so much about diving with a rebreather and how it is rapidly gaining popularity among the divers. Some of the positive comments include enjoying the “real” silent world and how such a compact unit can be more than 30 times more efficient than the conventional scuba unit. I had also processed numerous TDI rebreather certifications in the TDI regional office but yet I knew so little about these machines. All that I knew was that the rebreather operates by removing the carbon dioxide that we breather out and injects a certain amount of oxygen back into the system to sustain life hence very little or no gases are released out of the system making it extremely efficient.  Well, I am about to find out more.

On June 2009, I decided to enroll into the TDI Evolution Air Diluent Diver course with Simon Liddiard (TDI instructor trainer) at Blue Marin Dive in Gili Trawangan. This is a small island off Lombok, Indonesia where the only modes of transport on the island are bicycles and horse carts serving plying along many great restaurants and beach bars. Simon Liddiard is one of the most experienced rebreather divers in the region and was also one of the test divers on the Inspiration unit when it was launched years ago. I was very fortunate to be taught by him along with Will Goodman (TDI Trimix and Evolution instructor), who subsequently completed a World’s Longest Scuba Dive record attempt on 11 January 2010 for 48 hours and 8 minutes.

Before the course even began on the island, my task was to complete the reading of the Evolution manufacture’s manual and a TDI Inspiration/Evolution Rebreather manual. Together, these combine to over 250 pages of information with many new terminologies. I could only get a better understanding after my third reading or so, but this definitely proves to be a great help.

Day one of the course was fully devoted to the theoretical classroom session. The setting couldn’t be more perfect as we sat by the pool to review all the new information. My instructor could tell that I had done my homework back at home as emphasized by him many times. I could only imagine the stress of teaching the student all the terminologies and the numerous skill sets. The fun begins in the late afternoon when we started to “break apart” the rebreather to look into the intrigue of this life supporting machine. The most interesting part is looking into the “brain” of the unit and seeing all the small components that actually calculate the exact amount of oxygen needed to maintain the set PPO2 (time to brush up on Nitrox theory again). Even before we start using this rebreather next day, we have to fully disinfect the breathing hose and the counter lungs as saliva or bacteria might be trapped in these areas not visible by naked eyes. This alone took a couple of hours.

The second day of the course begins with the pool lesson. This isn’t an easy morning that I was expecting. First of all, the preparation starts around 2 hours before the pool session even begins. Everything from the integrity of the unit to the electronics of the unit had to be checked and rechecked again. This process is very similar to the checklist process I did when flying a light aircraft. I soon found that this meticulous process of assembly and disassemble plays a very important part of diving with the rebreather.

First hitting the water definitely felt strange. I felt extremely buoyant at first having to deal with 4 air cells (breathing hose, counterlungs, bladder and own lungs) but this was easily corrected by my instructor. The first few breaths I took using the rebreather were simply amazing. No bubbles, no noise, the real silent world. I could still hear the solenoid “firing” and injecting O2 into the loop if I pay attention to it. I could also almost clearly hear the conversations of people talking at the poolside. One of the most conscious things I was trying was to limit the amount of saliva that I disperse into the breathing hose as I had heard tales of that filling up to a cup after each rebreather dive, not to mention it would have cost me a few beers as well. One of the skills that got me confused initially is the removal of the breathing hose while I blew a constant stream of small bubbles out. While this is perfectly normal for open circuit diving, it isn’t ideal for closed circuit diving as air would be air wasted from the loop and would have to be replenished from the very small diluent bottle than we have. At the end of 2 hours of doing numerous skills, I was both mentally and physically drained.

The same afternoon was our first and second open water dives. Even though the pre-dive check of the unit had been done in the dive center, we do not have the luxury of sun bathing on the way to the dive site. There were more checks to be done on top of the typical “A, B, C, D, E” sequence to make sure the unit is in tip-top condition. I was briefed that during the descent, I might feel deprived of air as the increased ambient pressure cause a significant reduction in the volume of air in the breathing loop. However no amount of briefing could prepare me for the sudden feeling of sucking on an absolute empty tank. No problem, you just have to manually inject the diluent gas (air in this case) back into the breathing loop, controlling the descend while doing a VALSALVA MANEUVER equalization. I loved it already!

In the water, diving with the rebreather isn’t easy at all for the first few attempts. Lots of concentration had to be given to the handset to comprehend the displayed information. Of course there is always the Heads up Display (color lights in front of mask) and the buzzer to draw your attention when needed but that does not replace the need to check the handset frequently. A sew-saw profile have to be avoided as even a change in less than a meter would cause all the air cell to expand and you might end up on the surface before evening knowing it. In fact, this is one of the most expected scenarios that a novice rebreather diver might encounter. Many of the rebreather students felt quite demoralized after the first few dives, wondering if diving on a rebreather is for them. I had the exact same feeling as well but preserved on trusting that I would get better with more practice and it really paid off.

I soon discovered that the most unlikely piece of dive equipment to spoil a rebreather dive is a leaky mask, which I had over my first 3 dives. Fresh diluent had to be added into the breathing loop every time a mask clearing is executed as gas is released into the open. At the end of one dive, I had used about 300 liters of air which was unbelievable fast (this is about 20 bar of a 12 L tank filled to 200 bar). It was only when I switched to a proper working mask did I fully enjoy the efficiency of the rebreather.

Getting the course done in 4 days wasn’t easy at all. There was no time for slacking and I was really knocked out end of each diving day. As I dove more with the unit towards the end of the course, the more I began to appreciate the capabilities of the machine. Even though there was some negative publicity in the news about rebreather diving, it is not a lot more risky than conventional scuba. One example is that given the efficiency of the unit, you will almost always have more time and air left to fix problems underwater. Even in the unlikely event that the handset fails completely, you can operate the unit as a semi-closed circuit (recycling fresh diluent after every few breaths) which can be almost 3 times more efficient than a conventional scuba unit. During my training over the four days, both my instructor’s and mine Evolution unit performed flawlessly which in part was due to the thorough care given to it.

On the whole, the rebreather training had been a wonderful experience. The last 2 training dives on the unit could be described as the best dives I ever had. I felt like a giant stealth machine approaching the fishes and they were swimming over my head freely without any disturbances. On top of that, I felt very much in control of the unit and knew I could handle any contingencies that might occur. I am sure I would get the same amount of satisfaction training with any other model of rebreather given the right and competent instructor. As the saying goes, the quality of the instructor makes all the differences.

People often asked about my first experience diving with a rebreather. I would describe it like breathing in and out into a big flexible plastic bag while wearing a nitrox blending machine to support it. Simply awesome!!!

For a list of dive centers offering closed-circuit rebreather course, click here