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Arctic Dive Testing in Boden Sweden includes Poseidon SE7EN Rebreather

Poseidon Arctic Dive Testing in Boden, Sweden - Rebreather, Full Facemask, and Regulators


By Jonas Brandt, CTO at Poseidon


Rebreather in ice



Map of Boden

Poseidon R&D with Jonas Brandt & Jörgen Sahibzada went up to northern Sweden for extreme winter testing of our dive gear.  

The selected venue was the Lule river “Luleälven” located near the city of Boden right on the arctic circle (see map to the right).

We spent three days of diving, two dives per day. From a testing point of view we were very lucky based on the ambient conditions. We decided to test the rebreather “Poseidon SE7EN”, full face masks and open circuit regulators, mainly Xstream series and Cyklon series.



Forecast chart


Ambient conditions

The ambient air temperature was between -25°C to -30°C throughout the testing period. Water temperatures close to 0°C (average of 0.11°C, flowing fresh water). This is likely the most demanding conditions you can expose diving equipment to.





Preparations / Suiting Up

It is as important prior to diving that the equipment in total is well maintained with grease. Ambient temperatures as low as these causes any equipment to behave different than it would under normal conditions. We used Poseidon standard grease and O2 compatible grease.

We used Poseidon 3mm / 7mm drysiuits with 3 layers of undergarments in various thicknesses. Hoods and gloves in 5mm neoprene or insulated dry gloves. This was sufficient to stay warm at least 30 minutes, after an hour it became quite cold. The most challenging part is to keep your fingers warm.



Diver in water SE7EN

Day 1 – Rebreather testing


Two SE7EN units were prepared for testing, one unit was stored and conditioned inside at room temperature and the other was stored outside during the night in about -30°C.

What we learned from a set up point of view was that the systems behaved as intended. But from an ambient temperature point of view it is important to store the battery module and the O2 sensors in warm conditions, or they should be warmed prior to the pre dive test procedure.


Drysuit and bootsDiver on edgeAnother useful method to use when storing the unit in these conditions in between dives is to hang it in the water. The unit will then stay around zero degrees and you will not experience any icing issues. If there are icing issues it is also very useful to bring a thermos with hot water, the water can be used to de-ice if this occurs. To bring hot coffee is also good but not to pour on the equipment….



Shot from underwaterFinsDiving with the BCD connected in these conditions is a waste of time. Nothing in the inflator mechanism worked properly.
The only way to manage buoyancy is to use the dry suit inflator.






Day 2 – Rebreather testing

Full Facemask at surfaceSE7EN Rebreather with full facemask

Second day our tests continued. The conditions from day one were similar, slightly colder and now clear skies.

The tests from day one were repeated but the dive duration was 1h. We decided to focus on a full face mask implementation for the rebreather based on the Poseidon Atmoshpere. We dove the mask in a total of two separate dives were we used the method having the rebreather hanging on a rope in the wake.

This procedure works very well even if you have to be quite quick donning the equipment on land, but even when we were quick, the suit inflator hose froze almost immediately. Again, the thermos with the hot water was useful.


Day 3 – regulator testing

Last day we had prior to our trip planned to perform tests with our open circuit products. Under the existing circumstances, 0 deg water temp and -32 degree air temp the nature showed us that breathing simulators and climate chambers can't compete with pure arctic cold. The power of nature is brutal.


Regulator DetailThe tests consisted of a first dive with dry equipment followed by standard cold water diving procedures. The equipment (Xstream and Cyklon series) performed very well.


In the next phase of the tesing  we wanted to try to trigger free flowing equipment while diving, this was quite easy based on the cold ambient water which couldn't assist in warming up the regulator at all.



Diver at surface with regulator

Once we triggered the malfunctional regulator we continued to breath from the regulator to try to correct the free flowing regulator while diving. This excersise turned out to be successful. One of the insights is that it is advisable to practice valve actuated breathing prior to diving in extreme conditions.


The last phase of equipment testing began with the equipment being placed on the ice wet. Putting a regulator in such conditions is really not something that we would advise, but as a manufaturer and devloper it is really important to understand how, when, and why a product malfunctions and further find procedures for how to overcome the hurdles in extreme situations. To perform repeated dives, the access to hot water is again very useful for de-icing 1st and 2nd stages.


Cyklon with iceWe tested several regulators, and all regulators regardless of brand had free flows. To manage opem circuit diving, it is a matter of being accurate in pre dive procedures and to find a protocol that works for the diving equipment. We feel that we now have such protocols for all of our products for use in extreme environments.