Main IndexPhotos Draeger SM 1




Dräger SM 1

Date: 11 April 2005

Selbstmischendes Mischgas-Schwimmtauchgerät SM1

Database semi closed rebreathers by: J.W. Bech










Land of origin



Design year



Special Note: 

Rare rebreather


User group



Magnetic characteristics

Non Magnetic/ Acoustic


Part no:



Working principle

Constant Mass Flow

 Oxygen 2 ltr/min - Air 2,2 ltr/min

Gas type

Oxygen - Air


Oxygen is added by means of a first stage regulator with a fixed IP of 9 bar. Resulting in a constant oxygen flow of 2 l/min independent of the depth!

Air is added by means of a depth compensated first stage regulator AND a second stage regulator reducing the IP being 0,5 above ambient pressure. (depth compensated).







The gas is mixed in a mix tube before entering the loop. The system in supplied with two switches who guard the pressure between the restrictors, in this way warning the diver when the gas flow stops.







Intended use



Dimensions LxWxH

 640 x 420 x 270 mm


Device weight

 In Air 25 kg in water 4,0 kg


Intermediate Pressure

9 bar 02 fix/ Air Pamb+0,5 bar


Overpressure valve

 15 cm watercolum


Max depth

40 meters


Used material for housing/backplate

glass fibre


Pressure reducer

 Oxygen, fixed, Air depth compensated

 Air 2 staged pressure reduction 10bar - Amb+0.5 bar

Connection reducer – bottles

 Oxygen cylinder with inside thread, Air outside threat

 Aluminium bottles 1,5 ltr max 200 bar

Supply pressure

200 bar, minimum 30 bar


Umbilical connection



Color of cylinders Air : Gray, Oxygen: Blue  

Manual bypass

Yes, by pressing lever both gasses are added


pO2 measurement standard


Lamp guarding gasflow

Pressure gauge range

0-200 bar

Lamp fitted in mask


2 x 1,5 liter


Cylinder material



Cylinder thread

G 5/8” inside and outside





Designed for gasmix



Co2 absorption cartridge capacity

2,1  liter


Co2 absorption cartridge rechargeable



Co2 absorption cartridge storagetime

no data


Co2 absorption time testing (CE)



Connections Co2 cartridge

The scrubber is fixed in the rebreather housing


Guaranteed absorption time

 100 minutes @ 10 meter


Grade of absorption material

 no data


Breathing bag material

 inside rubberized


Inhale bag volume

no inhale breathing bag


Exhale bag volume

 10 liters fixed between exhale side and scrubber


Total loop Volume

Total volume 11 liter


Operating temperature

 no data


Magnetic signature



Colour (s)




On the back


FFM attached



Mouthpiece valve



Extra info:

Low acoustic signature


Safety device The unit comes with a double pressure switch. In case pressure of one of the gasses drops below a certain safety level the switch turns on a small lamp in the divers mask. You can see the small cable fixed on the mask.  

Additional information:  


Email address owner:



URL owner:



If you have any information to add this sheet please mail it to References to source and names will always be added!  


Info found: Ake Larsson, Tauchtechnik G. Haux, Original Manual Dräger SM1 kindly offered by Nautiek Diving Netherlands






 The unit is equipped with an oxygen and air bottle. Both bottles have a volume of 1,5 ltr and 200 bar working pressure. Mixing the oxygen and air is done automatically. The mix is changing with the depth. The carbon dioxide exhaled by the diver is removed chemically by the scrubber. The cleaned air is mixed with the ait-oxygen mix that is injected in the loop. The design is made in such way that 2 ltr/min oxygen consumption of the diver is possible. The lower fraction of oxygen pressure is restricted to 0,2 bar. When the diver uses 0,5 ltr oxygen per minut the unit will not provide gas with a higher partial pressure of oxygen above 2.0 bar. During a common use of 1,3 ltr/min oxygen consumption, the partial pressure of oxygen will be arround 1,5 bar.

Example: Suppose the diver dives to 10 mtrs depth and has filled his loop with gas. The starting percentage of the loop is 50% of oxygen. When using 2,0 ltr/min (graphic 1) after 30 minutes the oxygen % will drop to 20% and reaches the lower limit. At 10 mtrs waterdepth the loop lower limit is 10%. When using 2,5 ltr/min this lower limit is reached in 20 minutes (graphic curve 2). When using 3,0 ltr min in 10 min the lower limit is reached.



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