Closed-circuit Rebreathers Explained

Closed-circuit diving uses a rebreather and recycles the gases exhaled during the dive. Divers have a mouthpiece, a carbon dioxide scrubber, counter lungs, a gas tank, hoses, and an over-pressure valve. It’s a complex diving method but does offer more advantages for the experienced diver. Divers are able to reach greater depths than with open-circuit diving and that can make the experience even more enjoyable. Military and recreational divers often opt for rebreathers because they’re able to go beyond what open-circuit scuba breathers allow.

A closed-circuit diving rebreather can appeal to experienced divers since they’re able to remain in the water for longer. However, it’s not without its drawbacks. It does require certification to take part in rebreather diving; but, there are also many rewards for this type of diving too.

What Are Closed-circuit Rebreathers?

Closed-circuit rebreathers have made their mark on the world and have taken diving to a whole new level. Diving hasn’t been this exciting in years and divers from all parts of the globe are looking to get involved with rebreather diving. With rebreathers, there is now more freedom underwater and enables divers to get closer to nature than before. However, in order to become a qualified rebreather diver, additional training is required.

Training costs aren’t exactly cheap. It costs thousands to go through a rebreather training course. Once you’re certified, you have to buy the necessary equipment (if you want to go rebreather diving) and that’s another expense. Fortunately, there are many types of rebreathers available and you should be able to find a suitable one.

So how do rebreathers work? The rebreather uses a closed-loop breathing system. Every time you exhale, gases, like carbon dioxide, escape. However, the gas travels into the rebreather system and is then filtered so it can be reused as oxygen again. Unlike the open-circuit breathers, rebreathers prevent air bubbles from escaping while you’re underwater and that means there’s little disturbance to the marine life. Air bubbles only escape as you rise to the surface and oxygen pressure remains the same during the dive.


Adapting To This System Takes Time

You’re a competent diver and have over thirty hours of logged dive time behind you, but now you want to try technical diving. What do you know about it? Do you know what it takes to dive with a rebreather? Despite what you might believe, rebreather diving is very different from open-circuit diving. Your body may not be used to the system or how it works and that could impact your abilities underwater.

Divers who want to use rebreathers have to allow their body time to readjust to this way of diving. Remember, it’s a completely new way to breathe underwater (or rather a completely new breathing system) and some may even feel uneasy with it. For instance, the sensation of breathing underwater is very different from that of open-circuit breathers. There’s no noise from the rebreathers either (which can unsettle some) but has a feeling of high-pressure air. Also, the air isn’t released back into the water when exhaled and instead goes into the counter lung of the breathing equipment.

What that means is that you aren’t changing your buoyancy levels and it confuses some divers until they’re used to it. Of course, it’s offering a more natural underwater dive experience and tries to keep your breathing as natural as possible. However, that can open the door to problems during the ascent, especially for those who are used to diving with open-circuit breathers.

Divers require rebreather training. During training, they will learn everything they need to know about the rebreather and the equipment used alongside it. A diver will also use rebreathers during their trainer so they can get used to them; however, even then, a period of adjustment is required. A lot of divers forget that when they jump into rebreather diving and get the shock of their lives. Instead, ease into this type of diving and give your body time to get used to the breathing loop.

All Divers Must Undertake Rebreather Training

Rebreather training is an essential part of the diving process. Unfortunately, some divers don’t think certification is necessary; but jumping into this without proper training can be fatal. Diving is dangerous. If you aren’t properly trained you could get seriously hurt or even die. Okay, so while that sounds extreme, it has been known to happen. For the most part, diving fatalities come down to inexperience, gear malfunctions, and of course, running out of air. Even experienced divers run into difficulties at times and that’s why training is a must. Of course, training can’t prevent hypoxia or stop a diver getting the bends, but it may help them stay safer in the water.

Remember, experienced divers are at risk, just as much as inexperienced divers are when it comes to rebreathers. They put a strain on the body and require ample time to get used to as well. However, rebreathers must be used correctly to prevent an accident from happening. It utilizes a new breathing method for the diver, in a sense, and takes time to get used to; but, can ease the pressure your body feels as you go rebreather diving.

Diving breathe


The Advantages of Closed-Circuit Rebreathers

There are several advantages of rebreathers, including:

  • Dive Duration

How long can you dive when you use an open-circuit breather? Standard scuba diving gear can offer a fairly decent (and lengthy) dive time and should allow you to enjoy and explore the ocean floors. However, a rebreather enables you to spend far longer underwater. Rebreathers make a real difference because you can enjoy the experience and explore more.

For instance, you can spend possibly 3-hours or more (possibly up to 6-hours) on a single dive with a rebreather (exact times depend on the exact rebreather and oxygen tanks used). That really does give you enough time to explore any marine or sea life you want. You don’t need to change oxygen tanks over either and that’s fantastic. It’s a huge benefit and certainly one that appeals to divers everywhere. Of course, specific dive times depend on the model used.

However, Navy SEALs may be able to reach a dive depth of 70-feet or more. Dive depths vary for every individual diver and their specific skill level. Some experienced divers may feel comfortable around thirty feet with a rebreather and slowly move on to forty, fifty, and sixty feet depths. On the other hand, some fairly new divers may venture to a shorter depth level. Again, this varies and depends on the individual diver’s abilities and comfort zone.

  • Enjoy the Undisturbed Atmosphere

One of the best things about rebreathers is that they are far less intrusive for animals living in the oceans and seas. When you use a standard breather or an open-circuit breather, there will be gas bubbles released into the atmosphere every time you exhale. When that happens, fish can be scared off and it means you miss out on seeing them up close and in their natural habitat. This is a disadvantage for marine biologists and of course, marine photographers.

However, a rebreather changes all that. There are no air bubbles released because when you exhale, the gas is transferred in the system. You can enjoy viewing the fish doing what they normally would without batting an eyelid at your presents. It’s a wonderful experience.   

  • Use Less Helium And Save Money

Rebreather diving isn’t the most expensive hobby you can have; however, it’s not the cheapest either. You have to purchase gas such as oxygen and helium. However, helium is very pricy and that’s a problem for most divers. With a rebreather, less helium is used and that means you don’t have to purchase as much helium as you would normally. It’s a fantastic way to save money and a fantastic advantage of the rebreathers as well.

The Disadvantages of Rebreathers

Unfortunately, as with most things, there are a few drawbacks of using a rebreather, including:

  • Bailout Bottles Or A Failsafe

Bailout bottles are needed when you use a rebreather. Of course, this isn’t an absolute requirement for you to dive; however, for safety, a bailout bottle is necessary. This is a failsafe should the worst happen. If the rebreather breaks down or something happens and your air supply is cut-off, you have the backup oxygen to enable you to reach the surface in time. That’s a major drawback with the rebreather and something which some divers find frustrating. However, it’s very important to have bailout oxygen with you so you don’t run out of air.

  • Buoyancy Differs

With an open-circuit breather, you release oxygen every time you breathe and allow you to rise to the surface. It makes buoyancy a little easier and for most divers, that’s a great advantage. However, a rebreather doesn’t work in the same manner. Since there is little oxygen released into the ocean, it’ll require more work to balance your buoyancy and to rise. While it’s not a major issue for some divers, others will find it annoying. Also, it takes time to get used to it.

  • More Maintenance Is Required

While technical diving can be fun, it’s not without its issues. One of the worst things you have to consider is rebreather maintenance. Okay, so it’s not the worst problem you can run into, but it’s something that needs to be handled properly. Caring for your diving equipment is essential because if there is poor maintenance, it could result in a serious accident underwater. All equipment must be kept in good order and that also means additional prep and check time is required before every dive. It’s a drawback for some.

Rebreathers do have a few disadvantages to them but they also help determine who is really serious about rebreather diving and who isn’t.


Do You Dare Try Rebreathers?

Diving rebreathers offer some of the most unique advantages divers can find today. They allow you to reach depths you wouldn’t normally be able to and explore the seas without disturbing fish and other marine life. It’s an incredible experience and certainly something more experienced divers want to try.

Closed-circuit rebreathers are safe to use – however – proper training and education are required. Without training, divers shouldn’t use rebreathers because they’re dangerous pieces of equipment. If they fall into the wrong hands, it could be fatal and that’s why divers are required to have the necessary dive-log times behind them. The technology may be smart, but rebreathers still pose a risk.

Divers opting for rebreathers will find them ingenious in terms of how they run and being able to reuse the same gas and air supply is great. Rebreathers are some of the most useful, not to forget unique, tools divers have available to them. Closed-circuit rebreathers are easy to understand and can be safe if you’ve trained and become certified with them. A rebreather can offer a new way to explore the underwater kingdoms.