How Does a Rebreather Work in Diving?

Last Updated: August 9, 2022

Rebreathers can offer divers a completely new approach to appreciating the underwater world. Since the choice to enter the world of rebreather diving is a serious one, regardless of whether it is the technology or the possibility of swimming freely without producing bubbles that draws you, it’s important to know how this piece of diving equipment works.

Rebreathers are gas tanks that divers wear on their backs. While they look similar to standard diving equipment, this piece of equipment works to remove any carbon dioxide from the air, allowing the diver to breathe again. As a result, this piece of equipment can not only extend your diving times but can also allow you to explore the depths of the oceans further.

Continue reading to learn more about diving rebreathers, including what they are, how they work, as well as the different types, their advantages, disadvantages, and more.

What is a Rebreather?

Rebreathers are becoming increasingly popular among many new and professional divers. Also known as a CCUBA, or closed-circuit underwater breathing apparatus, this gadget works to remove carbon dioxide from the diver’s exhaled air.

The three main categories of rebreathers are classified as pure oxygen, semi-closed rebreathers (SCR), and closed-circuit recyclers (CCR).

Regardless of the rebreathing device you choose, this piece of equipment works to recycle any leftover breath. This air is then mixed with a tiny amount of oxygen or an oxygen-gas combination in order to enable a deeper dive with less reserved oxygen and a smaller tank.

Due to the recycling process, a diver using a rebreather will also produce significantly fewer bubbles than one using regular diving gear.

Overall, the diver may, therefore, scare away less aquatic life and stay at depth much longer with a rebreather than with conventional diving tanks.

How Does a Rebreather Work?

A rebreather’s main goal is to supply a diver with the ideal mixture of gas for breathing at any depth. It accomplishes this by keeping track of the oxygen level in the tank using a computer that is connected.

For example, when at various depths, a diver needs varying amounts of oxygen. A rebreather, therefore, works to keep track of the ideal amount and then blends it with the exhaled air in the tank.

Another component of the rebreather is known as the “scrubber.” This canister of sodium hydroxide gas absorbs the carbon dioxide in the exhaled air. A loop is then created when the air returns to the tank, where it is combined with oxygen and provided to the diver again.

What is The Main Purpose of a Rebreather?

The main purpose of a rebreather is to recycle any air exhaled by the diver in order to remove any carbon dioxide and infuse the air back with oxygen. These devices, therefore, not only work to extend diving times but also produce fewer bubbles, creating a blissful dive.

Why Do Divers Use Rebreathers?

Overall, the main reason why divers opt for the use of rebreathers over conventional equipment comes down to the easy gas fills and extended supply times offered by these devices.

For example, you can preserve your bailout tanks until you need them in an emergency and, if unused, there is no need to replenish them between dives. This means that even when diving many days in a row, all you need to worry about is filling your tiny onboard gas tank before you dive.

These devices are also known to take significantly less time and are known to be more convenient when attempting to get the perfect mix of gas for your next dive.

Types of Rebreathers

While all rebreathers accomplish the same objective to remove any extra CO2 from the breathing loop while supplying the required quantity of oxygen, the manner in which various types carry out this operation differs.

Remember that it is a substantial investment, therefore, it’s crucial that you take the time to discover the best rebreathing device that is appropriate for you and the diving you do.

The three primary categories of recyclers are commonly separated by the terms of pure oxygen, semi-closed rebreathers (SCR), and closed circuit recyclers (CCR).

1. Oxygen Rebreathers

In general, pure oxygen rebreathers are the most straightforward, since just one dive bottle is attached. The diver breathes pure oxygen from this bottle from inside the machine.

Lime is also used to filter any carbon dioxide in the air, and the bottle’s oxygen will replenish any O2 that the diver’s body has already used up. You can, therefore, rest assured you will always be able to breathe thanks to these rebreathers.

Take note, however, that the physiological characteristics of O2 are where this recycler’s limitations lie. Therefore, it is highly suggested to avoid using this sort of gadget at a depth of more than 6 metres.

These recyclers are also frequently worn in front of the diver’s body and are most commonly utilized by combat swimmers from various army forces across the world.

2. Semi-Closed Circuit Rebreathers (SCR)

semi closed circuit rebreather

There are several important ways that semi-closed rebreather systems differ from their fully closed counterparts. First of all, they only utilize one gas source as opposed to the two gas sources that are normally needed. This is typically a Nitrox mixture of 32 percent and higher.

When compared to utilizing the identical bottle in an open circuit, these devices have an average gain in autonomy of between 3 and 10. Semi-closed rebreathers are also said to be particularly dependable because they have minimal to no electronics.

Overall, other than a few speleologists and demining divers, these devices are less common today. Due to recent technology advancements, closed recyclers have, however, become more and more reliable to the point that they have supplanted semi-enclosed recyclers.

3. Fully-Closed Circuit Rebreathers (CCR)

Overall, a one-way breathing loop serves as the foundation of closed-circuit rebreathers (CCR). As a result, when using this device, one hose transports the diver’s gas exhalation to a CO2 scrubber, while another returns it to the diver’s mouth after being filtered, renewed, and recycled.

With CCRs, small quantities of oxygen are manually or mechanically injected into the exhaled gas to replace the oxygen that the diver has metabolized in order to maintain a consistent partial pressure of oxygen (ppO2). The scrubber in these devices also functions to absorb the diver’s carbon dioxide emissions. Throughout the dive, the breathing mixture’s composition is, therefore, constantly changing.

Military and scientific divers have long utilized these types of rebreathers, but more and more divers are making the conversion to CCRs every day. For example, these are well-liked by underwater photographers due to the advantages of (not) interacting with marine life.

Advantages of Using Rebreathers

Rebreathers Can Extend Diving Times

The ability to take part in lengthy dives due to its gas efficiency is a rebreather’s main advantage. For example, depending on the kind you choose, a single fill of a tiny gas cylinder or cylinders plus a CO2 scrubber can typically last for anywhere between one and six hours.

Overall, your gas duration on a rebreather is almost independent of depth, in contrast to open-circuit diving, thus you could theoretically spend the entire period at the bottom. They also work to allow for several dives on a single scrubber and cylinder fill.

Take note, however, that, using a rebreather will not protect you from decompression sickness and nitrogen narcosis. Although more advanced closed-circuit recyclers can change your gas mix to lessen the DCS risk, such hazards still exist.

Rebreathers Speed Up the Decompression Process

Rebreathers also work to shorten the duration of the decompression process by using the ideal gas mixture for the diver’s depth. As a result, at various depths, divers are provided with a gas mixture that contains pure oxygen to replace any lost oxygen as well as other gases based on the depth of the dive.

The rebreather unit can also add Nitrox or Heliox in the proper mixes to optimize the partial pressure of oxygen to keep the diver safe, as well as minimize nitrogen levels to reduce nitrogen absorption. This is in addition to replenishing any oxygen that has been depleted from exhaled air by the diver.

Rebreathers Do Not Emit Loud Bubbles, Allowing You to Get Closer to Marine Life

Rebreathers also have the advantage of being quieter than scuba breathing equipment, allowing you to approach marine life without disturbing it since these devices don’t emit loud exhaust bubbles. This enables divers to get closer to animals and enjoy scuba diving with them.

For example, sharks are known to approach divers who use rebreathers more closely since they don’t feel as threatened. Hammerhead sharks are cautious animals, and the bubbles from a diving unit tend to scare them away. As a result, in order to get near fish, like hammerheads, one may require the use of a rebreather.

Disadvantages of Using Rebreathers

Unfortunately, rebreathers also have a few drawbacks in addition to their numerous benefits.

They are more difficult to use than standard scuba diving gear. Therefore, learning is required in order to acquire the skills to utilize this equipment correctly.

A rebreather failure can go unnoticed and be deadly. When regular open-circuit regulators fail, it’s obvious straight away. But with rebreathers, the signs won’t be immediately clear if you don’t have proper gauges and monitors in place.

Since these pieces of diving equipment are also thought to be more expensive than the majority of traditional gear, the expense of purchase and maintenance can also be a drawback.


– How Long Can You Stay Underwater on a Rebreather?

Depending on the scrubber length and the CNS oxygen toxicity clock, you can often dive for 2-3 hours with a rebreather. The gas supply provided is another constraint that will determine how long you can dive.

Take note, however, that when using a rebreather, how hard you work during the dive will, overall, determine how long you can stay below the surface.

– How Do Rebreathers Remove CO2?

The air that is exhaled during a dive, by a diver using a rebreather, passes through a scrubber when it returns to the system. The scrubber removes CO2, and O2 is then added from an oxygen tank to replace it. Once the gas has the right mixture, it is rebreathed.

Overall, since CO2 in large quantities is toxic to human bodies, the removal of CO2 is crucial. If the rebreathing system fails to remove the CO2 from the exhaled breath, the CO2 concentration rises while the O2 concentration falls. The additional CO2 breathed could then trigger a stress reaction in the brain, resulting in the diver experiencing an increased breathing rate, causing them to panic.

– How Deep Can You Dive With a Rebreather?

Traditional dives are limited in depth because of the amount of pressure on the compressed oxygen in your tank. However, with a rebreather, your depth is not restricted by pressure because of the mix of gas and the nature of the rebreather tanks. Therefore, you can take longer and deeper dives with no restrictions.

– How Do You Refill a Rebreather?

Rebreather systems can occasionally be challenging when it comes to replenishing oxygen. On the one hand, it is relatively easy to refill semi-closed rebreathers. These types constantly introduce extremely tiny, precisely measured amounts of pre-mixed gas – typically nitrox – to the breathing loop.

On the other hand, certain cutting-edge closed-circuit systems incorporate several computer-controlled oxygen sensors that need meticulous setup and supervision.

– How Much Does a Rebreather Cost?

The cost of a rebreather can quickly become too high. After all, rebreathers can include a variety of extra attachments that raise the overall cost of the apparatus. Before using this diving equipment, further training is also necessary, thus, in turn, also raising the cost.

Overall, this piece of equipment is expensive. It can cost anywhere from few hundred dollars to like $7000, but there are numerous different versions. Due to this high cost, you should do your research and make some inquiries about the type of unit that would best suit your diving needs.

Final Thoughts

Rebreathers can provide divers with an entirely different perspective on how to appreciate the underwater environment. Take note, however, that it is crucial to understand how this piece of diving equipment works.

Rebreathers, which divers carry on their backs, are gas tanks that are designed to recycle your air as you breathe. Overall, its primary function is to provide a diver with the optimal gas mixture for breathing at any depth. It achieves this by utilizing a linked computer to monitor the oxygen level in the tank.

When a diver needs varied quantities of oxygen depending on the depth, a rebreather works to monitor the ideal oxygen concentration before mixing it with exhaled air in the tank.

The carbon dioxide in the exhaled air is also absorbed by the scrubber in the rebreather. As a result, when the air returns to the tank and is mixed with oxygen before being given to the diver once more, a loop is then formed.

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