Some people would like you to believe that closed-circuit rebreathers (CCRs) are the future of diving. All diving. For everyone. And while that may be true some day, today is not that day.
Nevertheless, the fact remains that there are divers for whom CCRs are a “nice to have” option, as well as divers for whom CCRs are all but essential. Could you be among them?
The answer to this question will depend on a number of factors, including:
Do the benefits of CCR diving outweigh the drawbacks, given your specific situation?
Are you a good candidate for CCR diving?
Is CCR diving something you are likely to enjoy?
Let’s take a look at each of these questions in greater detail.
CCR Benefits and Drawbacks
You may already be aware of many of the potential benefits CCRs offer, the complete list is impressive and includes:
Reduced size and weight. Even after you factor in the all-important open-circuit bailout bottles, a CCR-based system will generally weigh less and occupy less space than the open-circuit regulators and tanks you would need to provide comparable bottom time and range.
Gas efficiency. Each time you take a breath from open-circuit scuba, your body uses less than four percent of the gas you inhale. The rest is exhausted back into the water, never to be used again. This inherent inefficiency becomes even more pronounced the deeper you go. In contrast, rebreathers allow you to use nearly 100 percent of the gas you take with you, meaning that you need to carry substantially less gas. In fact, given the same amount of bottom time and the same work load, you will need no more gas at 60 m/200 ft when using a CCR than you will on a shallow reef dive.
Savings on helium. Helium, a gas essential for clear thinking on deeper dives, has become prohibitively expensive. Yet, if you dive open-circuit, most of that helium is wasted. With CCRs you need substantially less helium and very little is wasted.
Reduced deco. Because CCRs expose users to the lowest concentration of inert gas possible, regardless of depth, they keep required deco to an absolute minimum — and, on many dives, eliminate the need for deco altogether.
Warm, moist air. Passing through a restricted orifice, such as that found in an open-circuit regulator first stage, can substantially reduce a gas mixture’s temperature. This is why first stages are prone to freezing in cold water. It also does little to help keep divers warm. CCR divers, in contrast, rebreathe the same, warm gas mixture which, as an added benefit, has higher moisture content than normal open-circuit gas. This leads to warmer, happier divers.
Silence. CCRs are often characterized as being bubble-free. They aren’t; however, the amount of bubbles they produce is minimal compared to open circuit and are mostly a result of gas expansion on ascent. This can be a significant advantage when observing aquatic life that is normally spooked by bubbles.
Few things in life offer a plethora of benefits without extracting a price in return. CCRs are no exception. Among the drawbacks of CCR diving:
Expense. This, more than any other factor, prevents most divers from joining the rebreather club. The least expensive CCRs are still in the US$5,000 range; a more typical investment in equipment and training for most CCRs is at least twice that. And, even though CCR divers may save on gases such as helium, there are offsetting expenses for consumables such as CO2 absorbent and specialized batteries, as well as for items such as oxygen sensors, which need periodic replacement.
Complexity. Compared to the typical CCR, open-circuit scuba is almost idiot-simple. CCRs, in contrast, have more in common with the breathing packs used by NASA astronauts than they do with open circuit. This incredible level of complexity requires more time for training as well as for pre-dive preparation and post-dive maintenance. Quick and easy are not words generally associated with CCR diving.
Loss of breath control. Most open-circuit divers are not fully aware of how much they rely on breathing to control buoyancy until they try CCRs for the first time. On CCRs, breathing has no effect on overall buoyancy, as you are simply moving gas back and forth between your lungs and the unit’s counterlungs. You can’t lose buoyancy by exhaling or gain it by inhaling. On CCRs, buoyancy adjustments can only be made by adding or removing gas from your BC’s air cell. This just adds to the overall work load on CCRs.
Travel challenges. CCRs are not the easiest thing to travel with. You are looking at at least one additional checked bag — one the airlines may consider to be overweight. Then you have to consider your destination. Will there be absorbent available or will you need to bring it with you? Can the dive operation fill your O2 and diluent tanks (remember that you will need to empty them to fly)? What will you need to bring in the way of spare parts? Would it simply be easier and more cost effective to dive open circuit?
Risk. “This unit can kill you without warning.” One CCR manufacturer actually puts this on every CCR they make. It is not an exaggeration. With increased complexity comes increased risk. Rebreathers offer several ways to die which just aren’t factors when on open circuit. As such, they are way less forgiving of carelessness and operator error than open-circuit scuba is. If you lack the self discipline required to be a CCR diver you can, and eventually will, die — most likely from oxygen toxicity. And the worst thing about “toxing” is that you will most likely be aware of what is happening to you, but powerless to do anything about it.
Whether or not the benefits of CCR diving offset the drawbacks will depend entirely on your particular circumstances. As you can tell, the current state of CCRs offer little benefit to sport divers — even though we are beginning to see units aimed squarely at that market. CCR benefits tend to favor deeper diving and longer dives, particularly as divers approach or exceed depths of 50 m/165 ft or more.
The risks inherent in CCR diving cannot be overstated. Which leads us to the next question:
Are You a Good Candidate for CCR Diving?
There are numerous parallels between CCR diving and aviation — so many that, in fact, CCR divers frequently use aviation terminology when talking about rebreather diving. It is not unusual to hear CCR divers discuss “preflighting” their CCR or “flying” their unit.
Just as not everyone who can drive a car can safely pilot an airplane, not everyone who can dive open circuit is a good candidate for CCR diving. To see whether you are, you need to be able to answer several questions, including:
Do you have a legitimate need for a CCR? Rebreathers make very expensive toys and they are not as entertaining as some imagine. Unless you do (or plan to do) a significant amount of diving well in excess of 50 m/165 ft, or need to remain under water for hours on end, or work with aquatic life that is easily spooked by bubbles, it’s unlikely that you truly need a CCR.
Is CCR diving within your budget? Remember that you not only need to be able to afford the cost of the initial purchase and training, but also the ongoing costs of absorbent, oxygen sensors, specialized batteries and the added travel expenses.
How extensive is your diving knowledge and experience? Opinions vary as to how many logged dives you need before venturing into rebreather diving. The number, however, is likely well into three figures. Equally important, is an in-depth understanding of the impact of exposure to high concentrations of oxygen at depth. This is what the TDI Advanced Nitrox course was specifically designed to provide.
Do you possess the necessary discipline and commitment? This is the single most important prerequisite. CCR diving requires you to be exceptionally disciplined and committed. The consequences for lacking these attributes are simply too great. You have to be willing, for example, to spend up to 20 minutes or more “preflighting” your CCR before every dive, as well as for the necessary post-dive maintenance and care. Not everyone is this committed. If you are not, stick with open circuit.
And, finally, there is this very important question:
Is CCR Diving Something You Would Enjoy?
It would be foolish to invest the time, money and effort required to become a CCR diver only to discover you just plain didn’t like it. Fortunately, there is a way you can discover whether CCR diving may be for you without ever having to make that investment. It’s called the TDI Rebreather Discovery experience.
The Rebreather Discovery takes nothing more than a morning or afternoon. Its goal is not to teach you everything there is to know about rebreathers, but rather to get you in the water as quickly as possible so that you can experience CCR diving first hand.
It starts with your TDI instructor going over the basic parts and operation of a rebreather. In shallow water, your instructor will have you practice operating the mouthpiece and breathing from the loop. Then it is time to swim with the unit so that you can get a first-hand feel for what CCR diving is all about. Your TDI CCR instructor will be with you every step of the way.