Rebreathers are now becoming commonplace at dive resorts and on live aboard vessels. As a diver you may have already done several dives before even hearing the term and yet even more before ever seeing one firsthand. There is a lot about the mechanics and use that seem strange and difficult. In reality, however, rebreathers have been around a lot longer than conventional scuba and they are easier to use and understand than what you have imagined. These articles present an overview of rebreathers history and development, components and parts, and uses for rebreathers over three sections.
Section 1 – Rebreathers History & Development
Believe it or not the first idea of recycling air underwater came in the late 1670s with a design by Giovanni Borelli. He conceptualised circulating air in copper tubing cooled by seawater. He thought this would allow impurities (mainly carbon dioxide) to condense. Although his idea was never tested, he sparked further thought on the matter.
There were countless Europeans involved in design making for breathing apparatus after 1680, but it wasn’t until 1878 that an Englishman Henry Fleuss built the first functional closed circuit oxygen rebreather. Consisting of a stiff rubber mask with two breathing tubes, a flexible breathing bag filled with caustic potash and a copper tank pressurized with 30ata of oxygen this was the world’s first rebreather. It successfully helped diver Alexander Lambert close a flood gate in an underwater tunnel being built under the Severn River in 1880, where Lambert spent 90 minutes underwater at 12m.
Further rebreather development continued mainly for fire rescue, mine disasters and submarine escape over the next 30 some years. Notable among these designs are the Davis Submarine Escape Apparatus (DSEA) developed in the early 1900s and soon afterwards the Oxylithe. The Oxylithe was special in design as it used sodium oxylithe peroxide, a chemical which gives off oxygen as it absorbs carbon dioxide.
Other oxygen rebreathers emerging during this time period include the Proto, Salvus, Amphibian, and Mine Recovery Suit. Regardless of design and purpose, at this point most of them were short duration rebreathers, approximately for use up to 30 minutes, and using strictly oxygen as a breathing gas.
It was not until World War II that significant changes in rebreather design advanced. To start, scrubber size increased to allow longer submersion. The Italians, using patented ideas from the DSEA (Siebe Gorman company), developed their own effective closed circuit oxygen underwater breathing apparatus (CCOUBA). In addition, they also created the fin and rubber suit (Pirelli rubber manufacturers) that gave mobility to divers. They coined the term “frogman” for the appearance of these covert divers.
These frogmen were then seated upon human torpedoes (think motorbike like scooters with ballistic warheads attached to the front). Their mission was to drive 300 kg worth of explosives towards enemy warships and leave them there to detonate. Unfortunately, one of their first attempts at doing this in September 1941 against the British was vessel, HMS Barham, was unsuccessful. The British recovered their human torpedo and dive equipment. Lucky for the British, they now had new prototypes for advancing their own rebreather technologies.
Soon thereafter, the Chariot (a.k.a Human Torpedo) came about buy the British in 1941 with the intention of allowing soldiers up to six hours underwater to depths of 90 feet. Unfortunately, little regard was given to Paul Bert’s earlier work on oxygen toxicity (La Pression Barometrique) and several accidents related to CNS toxicity occurred. Afterwards, new standards of 30 feet maximum were established for fully oxygen rebreathers.
France and Germany were also making their own versions of submarine escape oxygen rebreathers during the same time, very similar in design to the DSEA. In Germany, Bernhard Dräger and his company were at the forefront of developing CCOUBA, namely with the Bade-Tauchretter and the Gegenlunge. After WWII Dräger continued development on military units but also developed one of the first recreational semi-closed rebreathers. France, on the other hand, more or less abandoned further development of closed circuit systems after the war and ventured into open circuit systems. The late Lt. Commander Javques Yves Cousteau began work on the demand regulator, the ‘Aqualung.’
Other countries also played a part in rebreather use, namely the USA, Japan and Russia, but since they were later players in the game, their technologies were similar to what was already available (except for the Japanese who developed their own Kamashio and Fukuryu) or their technologies were heavily protected.
Regardless of which country, nearly 99% of rebreather use up until the 1970s was by militaries. It makes sense not to share top-secret weapons with the general public. However, with the end of the Cold War and less imminent threat of nuclear war, militaries relaxed a bit and the rebreather finally moved into the hands of civilians and civilian manufacturers.
Today, we have mixed gas rebreathers, semi-closed rebreathers and also fully automatic rebreathers slowly. The evolution of closed circuit rebreathers for recreational use deserves its own discussion that is beyond the scope of this first section. Needless to say, rebreather diving is back in full force from its early days as their use for longer dives, photography and videography, and for extreme expedition dives are driving their continual evolution to be safer and more robust systems.References: “A History of Closed Circuit Oxygen Underwater Breathing Apparatus” by Dan Quick, May 1970