On this picture you see Dr. Hans Hass and his wife Lotte Hass wearing the predecessor of the Modell 138. The unit was modified to become the Modell 138 in the 1950 's 
Here you see the actual unit of Hans Hass. It was a modified "Gegenlunge"and was dived by Hans Hass untill 1950.
 If you want to read more about the unit please check out this page:
This was the unit that was used by Hermann Stelzner and Hans Hass to develop the later 138. 
The origin of the rebreather is the Draeger Gegenlunge and Kleintauchgerat. It was developped in the Spring of 1941. Hass and Stelzner changed the concept of the kleintauchgerat by removing the continues flow regulator and replacing it by a manual controlled oxygen valve. Also they decided to put the Counterlung on the back of the diver to achieve a more confortable way of diving. By moving the counterlung to the back of the diver they made it possible to swim with the unit. Before 1941 the common way of diving was by walking on the oceanfloor or by ascending and descending. A free swimming diver was a new development. After the second World War the oxygen rebreather was develloped further tot the Modell 138. It was sold by Barakuda in Germany for the sportsdiving market.


I would like to thank Ing. Michael  Jung of the Hans Hass Institute for his kind permission to use the shown photos
The Draeger manual has a nice workingprinciple drawing: 
You might notice that the inhale hose is on the divers right shoulder. 
The unit was sold with mouthpiece or Full face mask. 
The use of oxygen rebreathers showed the changing view on the exposure to high levels of oxygen. In 1942 the user of the gegenlunge was advised:
They could use the rebreather during 25 minutes in 15 MSW
Then in 1952 when the Modell 138 was realeased they advised:
The unit could be used at 25 meters of Depth during 10 minutes!
Accidents must have caused the factory to give a more moderate advice
In 1961 the factory  adviced the diver not to dive deeper than 10 meters, although, according to the handbook of the 138, hyperoxia was not so dangereous as hypoxia. The depth however was limited to 10 meters because there seem to be people who do not perceive muscle twisting arround the mouth and eyes.....
Here you find the Barakuda logo on a sportdivers Modell 138 (not on mine)
OK, now let us have a closer look at my unit 138 - 1228
Clearly visible the letter (1) 38 - 1228 It seems to me that this is production unit 1228
A complete 138 on my table ......
Overpressure valve on the outside
Overpressure valve on the inside. You are actually looking on the inside of the counterlung. This 60 year old material is of a unbelievable quality!
Top of the scrubber. There are some blue particles (origin?)
The valves are near the scrubber and in the hose.
Here you see the mouthpiece. It has an small eye on it. Guess were it was used for....
Unfortunately some parts show the marks of there age.... 
This oxygenbottle was not the original one. The original one was a 0,6 ltr bottle filled with 150 bar. With 90 ltr of oxygen the diving time was limited to 40 minutes. 
One of the main differences between this 138 and  the rebreather of Hans Hass is that the 138 had a constant oxygen flow of 0,9 ltr/min and a manual bypass. The oxygen was injected directly into the counterlung and the unit was provided with a non return valve. 
Pressure reducer 
The inside of the pressure reducer shows the adjustable flow screw 
Oxygen is added directly into the counterlung on the inhale side of the loop 
Here you see the complete oxygen feed assembly 
Scrubber lock. The lock is made in a really professional way. 
In the background the second boss in the house looks if everything is still OK 
Now you can see how the scrubber fits into the counterlung and uses two seals 
Spring loaded scrubber. The scrubber should be filled and tapped until the lime is 10 mm underneath the edge.
bottom of the scrubber 
Full scrubber cartridge and half scrubber cartridge....... 

Copyright Hans-Hass-Institut fŁr Submarine Forschung  und Tauchtechnik
Hans Hass with the unit between the Gegenlung and the Model 138 in a mirrored view as printed in many books!
I hope you enjoyed the small journey in time!
This page was only possible with the help of M. Jung and J. Harju
published 9-5-2010

Please sign my Guestbook
Email: jw.bech@quicknet.nl

I have read a lot about the famous Dršger Model 138. An oxygen rebreather not easy to find. The famous Hass rebreather is 60 years old now after it was developed bij Hermann Stelzner and Hans Hass in the 40 's. Now I am very pleased to have my own a Model 138. After years I finally managed to buy a 138 in the beginning of 2010. Here you find detailed pictures of the unit.

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