All you need to know about Rebreathers

Rebreather Diving = Silent Diving. One of the most dynamic trends in the new diving millennium will be the way we breathe underwater. Semi-closed Rebreather for recreational divers are here to stay - supported by PADI’s training programs for the Draeger Dolphin and Ray units. Enriched Air Nitrox has already proven to be a great asset for the recreational diver.

Why bother with all this rebreather stuff?

he answer is simple. If you want to go face to face with timid marine life for an extended period of time, without annoying bubbles, rebreather diving is for you. You dive into the water and in an instant you are in a different world. A Silent World. Stress, noise and the hustle and bustle of everyday life suddenly seem far away. You become one with the silent world and are acutely aware of your senses. No noisy valves, no hissing air, no annoying air bubbles - nothing. Even the ordinarily shy inhabitants of the sea are hardly bothered by your presence. And you are free to enjoy the fascinating feeling of being an accepted guest. For the first time you can experience the silence of the silent world.

You are diving with a rebreather. This allows you to experience diving as never before. What is special about rebreather systems is that your exhaled gas is not released into the water as in conventional open circuit systems, but is purified and returned to the breathing circuit. As a result, you can enjoy your dive to the fullest - not only a longer dive, but also a completely undisturbed adventure.

"Dräger Dolphin - a quite new diving experience"

The Dräger Dolphin removes carbon dioxide from the exhaled gas through a sodalime cartridge and then channels it into the inhalation bag, where it is enriched with fresh Nitrox from the supply cylinder.

This constant supply of fresh gas ensures that you will always be provided with enough oxygen. If, however, you should need more gas - for example if you are subjected to great physical exertion or you wish to clear your mask - a bypass valve opens automatically to supply additional fresh gas. For very shallow breathing - for instance if you are "lying in wait" for a photo opportunity - the circuit opens and small air bubbles escape almost silently through the positive pressure valve behind you.

Another aspect of rebreather diving you will enjoy is that the inhaled air is pleasantly warm and moist. This is because the chemical reaction involved in the absorption of carbon dioxide generates warmth and moisture, and as a result even ice diving can become a real joy!

As a result of optimal reuse of the exhaled gas, your gas consumption drops by up to 90%, meaning that the Dolphin's 4 or 5 liter cylinder can last for a whole weekend of diving.

"Nitrox - it's the mix that makes the difference"

The Dräger Dolphin uses Nitrox, in other words a nitrogen-oxygen mixture. Nitrox offers you a new range of diving. With Nitrox your breathing air contains less nitrogen, and you can stay down longer, because the non-decompression times have been increased. Say, you are diving up to a depth of 20 meters. Compared to a conventional non-decompression time dive with compressed air, Nitrox 50/50 enables you to stay under water more than 3 times as long!

How long you can dive, how often and how deep - with Dolphin this is all a question of the mixture. The variable oxygen-nitrogen mix ratio gives you enhanced capabilities. Extra training is essential though, to ensure that you learn how to take full advantage of these possibilities. We will be pleased to give you the training.

Benefits of using a Rebreather

Divers, over the years, met and solved many problems. Drysuits and quality wetsuits made it possible to keep cold further at bay, and larger and higher pressure cylinders encouraged dive times of one hour and more. The introduction of dive computers took much of the complication out of repetitive diving by making decompression calculations more straightforward, whether the diver wished either to make simple precautionary stops or more formal exposures.

The development and acceptance of enriched air NITROX diving offered longer and potentially safer dive times. But the amount of open circuit SCUBA equipment necessary to make most of this is too bulky, heavy and awkward for the average diver, making the extended dive time offered by NITROX a choice between submerging not only under water, but also under a massive pile of equipment! Open circuit SCUBA is also noisy and uncomfortable, the exhaust bubbles scare wildlife and interfere with vision, and the weight of equipment even makes getting in and out of the water inconvenient - and does little for the health of the diver's back!

Enter rebreather like the Dolphin; Lightweight, portable, simple to use, it revolutionizes NITROX diving. Extending dive time to up to ten times that offered by a conventional open scuba cylinder at normal work rates, reducing bubble noise to an absolute minimum (and hiding those few bubbles behind you), it allows you to get closer to marine wildlife (get this, photographers?), it allows you to pack hours of weekend diving into the boot of a car or the cabin of a yacht without having to wonder where the next air fill is coming from, and it allows you a freedom of access to the underwater world that you only dreamed of. It allows you to rediscover the sea down to 40 meters!

Utilization of breathing gas

Compared to the normal use of compressed air, NITROX breathing gases in a rebreather system has a much better utilization of breathing gas. With compressed air on a 20 meters dive we will have a utilization of 1.3%, the rest with 98,7% is lost. With a NITROX 50/50 dive at the same depth we will have a utilization of approx. 35%, depending on the work of breathing. If we go deeper we will also have a higher utilization with NITROX.

No decompression time

Most of the recreational divers are diving between 15 and 25 meters. Divers want to lie at the Great Barrier Reef at 15 meters to observe the underwater world and have the feeling of being with Captain Nemo 20.000 leagues under the sea.

NITROX gases will bring a great advantage to such dives. Depending on the choice of gas mixture, you will have longer non-decompression times, as with traditional compressed air. You will have the possibility to dive up to two hours at 20 meters without any decompression time. The limitation in this case is only the NITROX cylinder of the Dolphin with 4 liters and 200 bars.

Diving profile

A dive to a depth of 20 meters using compressed air, compared to the use of NITROX with 50% oxygen and 50% nitrogen, explains the big difference.

A non-decompression dive with a NITROX of 50/50 will extend the duration by more than 100%. Total duration of 40 minutes with compressed air will be increased to approx. 110 minutes with NITROX 50/50. A dive on 30 meters with decompression and a NITROX of 40/60 will impressively increase the bottom time and require a remarkable shortened decompression time.

Temperature of inhalation gas

When we compare the inhalation breathing gas temperature and open circuit system and rebreather, we will notice a real difference, which allows us to dive with a rebreather in January in Scandinavia without a freezing regulator. The heat generated in the scrubber canister causes this longer thermal balance.

We can further influence the inhalation breathing gas temperature with an insulator or a heater. But these solutions are being better applied in the field of commercial and military diving.

Different Rebreathers

When we talk about Rebreather, we must differentiate between four types of rebreather Closed circuit and Semi-closed circuit systems and pure gas, pre-mixed and self-mixing.

Oxygen Closed circuit rebreather

The exhaled breathing gas is cleaned in a closed-circuit system through a sodalime cartridge and is enriched with oxygen supplied from a cylinder carried by the diver. This apparatus is completely bubble-free with low gas consumption. The operating depth is limited by the use of oxygen. Therefore we do not use the oxygen rebreather for recreational diving, mostly it is used in military diving, because we cannot limit the sports divers to a maximum depth of 7 meters. We all know our friends - if they discover something interesting in the underwater world they will go deeper.

Mixed-gas rebreather

Mixed-gas closed-circuit diving apparatus facilitates long and deep diving operations. It operates as a Semi-closed circuit system with pre-mixed gases or a self-mixing system. Low gas consumption, safe decompression, longer no-decompression time, silent and less bubbles, are only some advantages of Rebreather, which recycle the exhaled breathing gas with a sodalime canister. Depending on the gases used such as NITROX or HELIOX diving depths up to 100 meters are possible. Specific features for special navy operations are provided in this apparatus, which should not be, confused with mixed-gas closed-circuit diving apparatus for sports divers.

History of Rebreather

  • 1889 - The Patent for a pressure reducer valve, made out in the name of Dräger and Gerling was the start in the year of 1889. This was a major development for Dräger and all other companies, who were involved in breathing, especially in diving - technology.
  • 1907 - The Rescue from sunk sub-marines using Dräger rescue diving equipment was the first step in the development of a full range of diving apparatus.
  • 1911 - Dr. Ing. h.c. Bernhard Dräger attempts the first diving tests. The target: to develop hoseless diving apparatus without a supply from the surface.
  • 1912 - Dräges product range included three types of hose- free helmet diving systems to be carried by the diver.
  • 1913/14 - The Drägerwerk diver test station for testing of diving apparatus. On July 17, 1914 for the first time people could live under a pressure of 9 bar (approx. 80 m depth) for 40 minutes. The first version of the Dräger diving table was developed. This was the first time that we got the experience of how the underwater pressure influences the diver's body and organs.
  • 1926 - A further development was the Oxygen closed-circuit diving apparatus for rescue diving, called "Badetauchretter". This was before swim diving. The diver walked under water. It was already a rebreather system with the main components breathing bag, sodalime canister and oxygen cylinder. Nearly the same basic technology we are using today.
  • 1952 - a small diving apparatus, called "Kleintauchgerät 138" - a pioneer of the closed-circuit diving apparatus was in the Dräger program. This rebreather was influenced by the work with Hans Hass and was a very important milestone for all later Rebreathers.
  • 1953 - A further development was the well-known closed-circuit diving apparatus "Leutnant Lund II" in the year of 1953. This unit is a real rarity in the world of diving and still in operation with some happy recreational divers. 1969 - Dräger added the rebreather range a mixed gas closed-circuit diving apparatus, called SMS I, for exciting diving bells. It was a bailout system with a self-mixing system. The parallel development of the SM I was the first autonomous rebreather with a self-mixing system.
  • 1969 - The well-known rebreather FGT I with Semi-closed system started in the Dräger program. Many different navies all over the world have successfully used this pre-mixed rebreather for more than 25 years for mine clearance purposes.
  • 1975 - Oxygen Rebreather LAR V for special diving operations started in the Dräger program. A successor of the well-known LAR III. This closed-circuit rebreather is standard equipment for many special forces and other navy groups all over the world.
  • 1984 - The deep-diving-system CCBS - Closed Circuit Breathing System - for depths up to 600 meters was developed as a bail-out unit for saturation diving in 1984. Dräger has built about 30 to 40 deep-diving saturation systems, complete with decompression chambers and diving bell. These have been successfully used in the oil- and Offshore industry for diving depths up to 600 meters.
  • 1994 - after several experiments with fully closed and computerized Rebreather, Dräger put the self-mixing closed-circuit rebreather M 100 M for depths up to 100 meters into the market. This rebreather has been designed for mine clearance diving in military field and not for leisure purposes.
  • 1995 - the Semi-closed rebreather Dolphin, especially designed for the recreational diving market, is released.