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What Is Rebreather Diving?

   February 11th, 2024   Posted In: Articles   Tags:

There are many ways to configure your gear for SCUBA diving. The most common way is via open-circuit SCUBA, but closed-circuit SCUBA in rebreather diving has become more popular in recent years. Rebreathers are very popular with technical SCUBA divers, but today, even recreational SCUBA divers can enjoy the advantages of rebreathers. What exactly is rebreather diving?

Before we define what rebreather diving is, let’s first take a look at the different systems used in SCUBA diving.

Open-Circuit System

First, let’s define the common way to SCUBA dive with an open-circuit system. With this system, you have a tank attached to you that contains your choice of gas (air, enriched air nitrox, tri-mix). You breathe through this gas via hoses attached to the first stage at the tank. The other end of the hose is the second stage which is a regulator that you put in your mouth to breathe from.

When you inhale, gas is delivered from the tank directly to your mouth. When you exhale, the carbon dioxide in your breath escapes out of the regulator and into the water creating bubbles. There are levers inside of the regulator that allow for the switching mechanism between the inhale and exhale. Importantly, no gas is recycled back to you. It is lost to the water in your exhale.

Closed-Circuit System

When you think about what rebreather diving is, you will think of the closed-circuit SCUBA system. In this system, the breathing gas is recycled and not lost to the ocean upon exhalation. Just like in open-circuit SCUBA diving, there is a hose that connects to the tank that delivers gas upon inhalation through a mouthpiece connected to the hose.

When you exhale, the breath stays in the hose and gets recycled back to the carbon dioxide scrubber. Once the carbon dioxide is removed, the remaining oxygen is sent to what is called the counter-lung. Your breathing gas is recycled in closed-circuit systems.

Semi-Closed Circuit System

There are some rebreathers that are called semi-closed systems because they have a pressure release valve that allows carbon dioxide to escape. However, there are still virtually no bubbles with this system. Semi-closed circuits use nitrox as the gas source. With this system, gas can last about 5-7x longer than open-circuit SCUBA.

Rebreather Equipment

While rebreathers contain some similar pieces of equipment as in open-circuit SCUBA, like a mouthpiece, hoses, and a gas tank, these pieces are slightly different for rebreather pieces. For example, the tanks are smaller. Additionally, the following are also common pieces of equipment in rebreathers:

  1. Counterlungs. The counterlungs act as close as possible to your actual lungs. They deliver gas through inhaling and exhaling by the diver using the same pressure as the diver’s lungs.
  2. Carbon dioxide scrubber. This very important piece of equipment removes the carbon dioxide from your exhaled breath and recycles the oxygen back to the system for use.
  3. Oxygen sensor. The oxygen sensor alarm is probably one of the most important safety features in a rebreather system. This sensor monitors the amount of oxygen available in the breathing supply tank. If this sensor fails, the oxygen levels could drop too low and cause you to pass out while diving. 

Rebreather Diving Cost

SCUBA diving equipment costs vary depending on the piece and model. In rebreather diving, every piece of equipment is significantly increased in price. People spend upwards of $10,000 and more on rebreather gear while in open-circuit SCUBA, a good system with regulators, hoses, tank, and buoyancy control device would cost around $2000 and upwards. Again, costs vary greatly depending on the models.

Why Rebreather Diving?

With the cost and all the added features of rebreather diving, why is it becoming more and more popular? The biggest reason is that it provides increased bottom time. How much more time underwater is dependent on many factors such as depth, currents, temperatures, and person. However, typical dives on rebreathers are usually in the 2-3 hour range, again depending on depth. 

No Bubbles

When we think of what is rebreather diving, no bubbles also come to mind. This is one of the reasons divers switch to rebreathers. There is a peaceful calm in rebreather diving where there is no noise upon exhalation. No bubbles also can lead to better visibility. This is also important when diving in overhead environments such as caves or wrecks.

Rebreathers offer the best advantage here because bubbles that escape in open circuit SCUBA units could hit the surface of the cave or wreck leading to reduced visibility and sometimes black outs which can be very disorienting and dangerous.

Recreational SCUBA Diving

Rebreathers used to be solely for the technical diving field. However, in recent years, rebreathers have gotten many new designs, and some have been added to recreational friendly dive courses. You can now train with organizations such as PADI to get rebreather certified.

There you have it. What is rebreather diving? It is the opportunity to get more bottom time and a better experience without the bubbles in your face using very specialized equipment. If you are SCUBA certified and looking for your next learning experience, why not try rebreather diving? As always, safety is important and proper training by professionals is needed before attempting to dive with a rebreather. Your life depends on it!

Candace is an avid scuba diver and freelance writer with a PhD in Biomedicine. She has been diving since 2002 and is currently a PADI IDC Staff Instructor. When she is not instructing, she enjoys writing about scuba and volunteering at the local aquarium where she dives with the sharks!

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