Contrary to popular belief rebreathers are actually a much older scuba diving technology than open circuit regulators The Long (his)Story About focus Scrubbers & Sensors From Fleuss to Evolution There is more and more talk of Text: Michel Tagliati rebreathers, stated Additional reporting by Peter Symes as being the future of diving. However, not many people have tried them. So what is all the fuss about? he greatest majority of the Treaders of this magazine will have learned to dive with a regulator originating from the Aqualung, which the renowned Jacques Cousteau and Emile Gagnan invented in 1940. The regulator was the first Henry Fleuss, an English naval offic- commercial, er from Germany, worked out the generally principles for a re-breathing appa- available dive- ratus, and produced a prototype at the system, and end of the 1870’s. He stayed down in a this promoted to re-use the air that has been exhaled, water tank for nearly an hour, and later the later great circuit, because the exhaled air by using a closed system. went down to 5 meters in a lake using expansion of piece of passes straight out into the surrounding his system. Fleuss was the first “diver” in sports diving equipment. It is reli- water, and is thereby lost. As only about Closed circuit systems history with a re-breathing apparatus. At everywhere. able, more or less foolproof, a quarter of the available oxygen has Closed circuit systems are a far from the beginning of the 1900’s the military And it must and its simple construction is been taken up by the body, and the rest new idea. It was Giovanni Borelli in the were quick to take up this idea. Oxygen- be said that very robust. These are good properties expelled, it is a rather ineffective utilisa- 1700’s who first thought of re-using the rebreathing equipment consisted of the regula- to have when one’s underwater breath- tion of a scanty resource. (See table next exhaled air. His idea was to recirculate an oxygen tank together with a bag of WWW.AMBIENTPRESSUREDIVING.COM tor is a fine ing depends on them. However, as we page.) the air through a copper tube which was potassium hydroxide and a breathing will see, there are also a number of dis- In addition, as the amount of air used cooled by the sea water, and thereby loop, and was used to rescue submarine Ambient Pressure Diving’s Closed Circuit advantages. And it is these that make increases proportionally with depth, open “cleaned” the air before re-use. Luckily, crews and attack divers (there were no Rebreather Evolution is the latest step in CCR re-breathers an interesting alternative systems become more and more ineffi- it was never made. The mining industry revealing bubbles on the surface). The ...erh... evolution. system. cient, and there are therefore major limi- and its problems with gas in the mine German manufacturer Dräger released When diving with a regulator, it is tations to how long a diver can remain shafts also stimulated the relevant tech- several models for military use in connec- said that one is diving with an open underwater. It seems obvious, then, to try nical developments during the 1700’s. tion with World Wars I and II. 82 X-RAY MAG : 4 : 2005 EDITORIAL FEATURES TRAVEL NEWS EQUIPMENT BOOKS SCIENCE & ECOLOGY EDUCATION PROFILES PORTFOLIO CLASSIFIED Respiration corresponding increase in A REBREATHER TIMELINE In a modern medical textbook on physi- pressure. Therefore, when 1500´s In England and France, full diving ology, one of the several chapters on using a closed circuit there 125 l/min suits made of leather with metal helmets. The aspects of respiration is entitled “Physical is the same consumption of diving helmets were already some sort of principles of gaseous exchange; diffusion air, whatever the depth. At 100 l/min rebreather, but needed surface supply and of oxygen and carbon dioxide through rest, 0.3 to 0.5 liters of oxy- were without scrubber 75 l/min the respiratory membrane”. And it is these gen are used per minute 1680 Giovanni Borelli designed a closed very important principles that are of great (l/min), and with maxmum 50 l/min breathing circuit. The idea was to recirculate interest to divers. How we take in and work up to 3.0 l/min are Open systems - i.e. regulator and tank 25 l/min air through a copper tube which was cooled utilise oxygen, and how we get rid of the used. Of course, there are Closed circuit rebreathers by sea water. The assumption was that al the 3 l/min carbon dioxide produced by metabolism. differences between indi- Gas consumption impurities would then condense out of the air viduals, depending on the 10m 20m 30m 40m inside the tube. Cellular metabolism is size of the diver and his or Depth 1726 Stephen Hale designed the first independent of pressure her physical condition. scrubber: a flannel liner, soaked in salt and The amount of air which is needed to Comparison of gas consumption in open and tarter, used in a helmet for mine disasters. closed systems. In closed circuit rebreathers the take a normal breath at a depth of 20 The carbon dioxide 1772-4 Oxygen independently discovered gas consumption doesn’t vary with depth. meters is three times greater than at the problem by Swedish chemist, Carl Wilhelm Scheele, in surface, and therefore the consumption As we have seen, cellular 1772, and the English chemist Joseph Priestly, of air with open systems increases with metabolism depends on oxygen, which diver can tolerate a build up to a CO2 in 1774. Soon followed the first known ideas depth. However, more importantly, cel- is inhaled from the atmosphere. The fol- concentration of about 10%, increasing to use Oxygen for diving and first functional lular metabolism does not depend on the lowing table gives the composition, in respiratory volume to compensate for ideas to build autonomous rebreathers. pressure. volume percent, of inhaled atmospheric the increased CO2. However, beyond 1876 Henry Fleuss began to develop an Oxygen is required to make adenosin air (on an average cool, clear day), and the 10% level the respiratory center in the oxygen rebreather. He used a rubber face trifostat, ATP, the fuel of the human cell. also the corresponding composition of brain stem begins to be depressed rather mask and a breathing bag connected to And a molecule of oxygen is a molecule exhaled air. (There is also a minor content than stimulated, and the diver’s respira- a copper oxygen tank. The carbon dioxide, of oxygen, wherever it is to be found, at of the non-reactive noble gases such tion then actually begins to fall rather scrubber was a rope yarn soaked in a solu- the beach, or 100 meters deep, with the as argon, helium, etc., but this has been than to compensate. As a result of this, tion of caustic potash. Enabling Fleuss to walk ignored here.) It will be seen that the varying degrees of lethargy, narcosis, along a river, this was the first SCUBA Dive. uptake of oxygen in the lungs has caused and, finally, anesthesia will occur. The 1879 Fleuss builds a Mining-Rescue the oxygen content of the inhaled air CO2 in the exhaled air must therefore be Rebreather for Siebe/Gorman to be reduced from its original 20.84% removed before the remaining oxygen 1881 A special rebreather scrubber using to 15.7% in the exhaled air. It will also be can be re-used. Luckily, this is quite easy a barium hydroxide is patented by Khotinsky seen that the concentration of carbon to do, using calcium hydroxide, Ca(OH)2, and Lake. dioxide, a biproduct of metabolism, has which reacts with, and therefore fixes, the 1904 Siebe and Gorman patent Oxylite, a gone up by about ninety times, to 3.6%. carbon dioxide. It is called CO2-scrub- potassium- and sodium-peroxide mixture that bing and the filtering material, in this case produces oxygen on contact with water. COMPONENT INHALED AIR % EXHALED AIR % teh calcium hydroxide, which comes as 1907 A Dräger rebreather is used as sub- N2 78.62 74.5 a granulate, is referred to as the scrub- O 20.84 15.7 marine rescue equipment 2 ber. CO 0.04 3.6 2 1912 Dräger helmet-diving-rebreathers are H O 0.50 6.2 In a rebreather, CO2-scrub- 2 available Total 100.0 100.0 bing therefore takes place by circulating the breathing gas 1913 Dräger performs a successful simu- So, it is not so much the reduction in through a canister with the lated 40 minute dive to 80m in chamber. amount of oxygen that is the problem, for scrubber granulate in it. 1914 Dräger introduce a selfmixing Nitrox- there is still some 16% available in each Rebreather for max. 40m. expelled breath, which should be avail- Scrubber, in this case 1926 Dräger presents the first early recrea- able for re-use. It is the increase in carbon Sofnolime, comes in tional rebreather, the ‘Bade-tauchretter’. dioxide, CO2, that is the real problem. A small granules, 1941 Dräger “Kleintauchgerät 138” 1953 Dräger Leutnant Lund II and No, rebreathers are not new. In this Expression: Breathing loop Barakuda Delphin I 1912-footage we see Drägers helmet The whole volume of circulating gas in a rebreather, mainly 1967 Russians experiments with predeces- diving rebreather in use. the hoses, one or two counterlungs and also the diver’s lungs. sor to AKA-60 Photo: Dräger’s archive.