Jan Jahns SMS 1

Jan Jahns used orifices from a furnace to build his SCR

The SMS 1 and SMS 1B where made by the German company Dräger in 1969. Originally designed as a lockout rebreather, the rebreather is now sometimes used as a SC rebreather.  The gas supply  was organised through a MVB III B mixed gas unit. A surface supply unit. In the rebreather was a small bailout cylinder for emergency situations.  The scrubber was a 3 hour design. Maximum operating depth 200 meters. Here you find nice pictures of Jan Jahn´s SMS 1.
This particular unit was mainly used in sweet water.

This unit was used with supply hose not from a UW cabin (as should originally be) but from surface in a deep freshwater dam. That is why an adaptor was used (the supply hose came from surface so it was connected in the upper part of the rebreather). I have removed the adapter by drilling off the screws (they were covered by a thick layer of epoxy) and that is why you can see a red tape inside the frame and white spots (I have not painted the plugs yet) on its outer side. I use the SMS1 recently as a SCR  wearing two 2-7 l bottles in stage positions with different mixtures (bottom mix and DC mix) with regulators on each and with the IP (changes a little with depth) from both leading into a manifold with exchangeable nozzles (I use nozzles from LPG ovens -0.13…0.32 mm diameter).  

In spite of opinions expressed in the rebreather-conference if possible I use the saver with 1/2 the volume of the original scrubber volume as can be seen in the detailed picture of the scrubber. As I am a physicist, I can calculate everything I need including nozzle diameters, dosing, concentrations as well as decompression (I use ZHL16 + Gradient Factors from Deco-planner).

Jan Jahns

picture: courtesy Dräger

Scrubber with 1/2 fill adapter.

Jan, thanks for your contribution and interesting remake of this rebreather!