If you love diving with open circuit SCUBA equipment and want to take your dives to the next level, consider taking a rebreather course. Not only will you need to lug less gear around, you’ll also be able to enjoy longer bottom time, particularly if you stick with fairly shallow dive sites. If you enjoy cave diving, exploring remote wrecks, or heading into deep water, you’ll find that the newest rebreathers take some of the worry about expending air out of the equation, leaving you with a greater capacity to enjoy your dive. Here, we’ll take a closer look at rebreather diving.
How Rebreathers Work
Rebreathers are fairly basic mechanisms which were originally developed by the military, and they are relatively easy to learn to use. With a rebreather, there is no need for cylinders of gas. Though a rebreather contains a large supply of breathing gas, the gas it contains is highly compressed, which makes the apparatus much less bulky than a standard kit.
As you breathe, your body takes in oxygen and expels carbon dioxide and other gases, along with oxygen which wasn’t absorbed by your lungs during the inhale cycle. The rebreather absorbs all of those gases and scrubs the oxygen particles, making them suitable for re-inhalation. The newest models automatically maintain your oxygen levels for safety at any depth, constantly varying breathing gas volume percentages while maintaining consistent oxygen partial pressure.
If you’ve progressed beyond Explore Scuba, you’re probably well aware that there are a number of gas mixtures available for recreational and technical diving. Just as you can obtain special mixes for standard cylinders, you can dive with a rebreather that has the capacity to deliver different gases. Many models allow deep divers to select helium or neon gas to reduce the potential for nitrogen narcosis.
There are three distinct types of rebreathers, and there are a variety of models on the market.
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Oxygen Rebreathers – A cylinder of pure oxygen serves as the gas supply. These rebreathers may be used only at no decompression depths, and they come with a danger of oxygen toxicity.
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Semi-closed Circuit Rebreathers – These rebreathers work with a variety of gas mixtures, and they enable you to enjoy diving at deeper depths without risk of oxygen toxicity.
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Closed-circuit Rebreathers – These are the most advanced rebreathers. They carry mixed gases and pure oxygen.
Most rebreather equipment consists of the following basic parts:
- Loop – The loop facilitates steady inhalation and exhalation, and it serves as a link to additional components within the unit.
- Gas Source – Depending on the rebreather type, the gas contained in the rebreather’s gas source is either pure or a mixture of breathing gas. Small amounts of new gas are added to the scrubbed air as needed.
- Carbon Dioxide Scrubber - One of the most important components of a rebreather is the Carbon Dioxide scrubber. This mechanism separates the Carbon Dioxide from the other gases, then absorbs it to prevent Carbon Dioxide poisoning. After scrubbing the remaining gases are worked back into the breathing blend.
- Counterlung – This mechanism is incorporated into the loop. It expands and contracts as the diver inhales and exhales.
- Bailout – The bailout is intended for emergency use in the event the equipment malfunctions or another problem develops underwater. It allows the diver to reach the surface faster and with a greater margin of safety.
- Casing – The casing contains the rebreather’s main parts. It is vented to allow for changes in pressure and volume.
- Diffuser – The diffuser is located over the blowoff valve. Its purpose is to diffuse any air which is released, thereby preventing bubbles from revealing the diver’s presence.
- Integrated Decompression Computer – This component monitors the breathing gas, tracking oxygen content and working out a schedule for decompression stops.
The Rebreather Training and Certification Process
Needless to say, it would be foolhardy to go buy a rebreather, strap it on, and head out for an adventure; in fact, in most places, you must either show proof of training to purchase a unit, or you may purchase your rebreather unit in conjunction with a rebreather course.
During basic rebreather training, you’ll learn how to assemble and pre-dive the unit, follow basic unit-specific checklists, and safely bail out, among other key skills. Basic rebreather diver training certifies you to dive to 60 feet within no deco limits.
Advanced rebreather training lets you take things further. Once you’ve been certified as a basic rebreather diver, you are eligible to certify for deeper dives to 100 feet within no deco limits. You will also learn how to rig and carry an offboard bailout cylinder to support the deeper dives.
If you’d like to roll both basic and advanced rebreather training into one course, you can do so with integrated course rebreather diver training, which combines all skills from both courses, and which certifies you to dive to 100 feet within no deco limits.
Many scuba centers that offer rebreather training also offer rebreather qualifier courses, which are designed for divers who are already certified on a certain rebreather unit, but who are changing to a different unit. These courses offer basic familiarization with the new unit, and are indispensable to ensuring you stay safe while learning the ins and outs of unfamiliar equipment.
Rebreather Advantages
If you long to enjoy deep dives but hate knowing that the majority of your underwater time is going to be spent on decompression, you’ll be happy to know that rebreathers minimize decompression obligations by optimizing gas usage. This is just the first of several advantages to diving with a rebreather.
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Improved gas efficiency – With conventional scuba gear, you exhale much of the gas you inhale, effectively wasting oxygen rather than consuming it. With a rebreather, you waste no gas whatsoever.
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Lighter equipment – Compressed air contains 78 percent nitrogen, which makes up most of the weight in a conventional cylinder. Since rebreathers operate without nitrogen, they weigh much less.
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Underwater stealth – One reason so many military divers use rebreathers is that there are no bubbles to reveal their presence. Without bubbles, it’s easier for recreational divers to blend into the environment so marine life will not be disturbed.
Now that you know a bit more about rebreathers and rebreather training, consider taking your dives to the next level. With training and experience, you’ll be able to enjoy diving even more than you do today.