Working in sub-zero temperatures is always challenging. How would the rebreathers cope? Luckily Carl had managed negotiate the use of two Royal Navy Mine Hunters for the duration of the project and after an epic drive the length of Norway by Carl (I am not bloody doing that again) Spencer, we loaded a stuffed full transit’s worth of kit onto HMS Quorn. Transits are not known for their Winter road holding capabilities and this one was no exception. Fifteen hundred miles driving through a Norwegian Winter, just about broke it and it did break Carl.

We were allocated a below deck stowage/kit prep area, the only heating came from Al’s head light. Luckily this compartment stayed just above freezing, so we could safely store the rigs here. One major issue was sofnolime freezing. We knew from CE testing, that the units could handle -20 degrees C, but any moisture in the sofnolime would freeze within a matter of minutes. We combated this in several ways.

The general protocol was always to dispose of a canister after each dive. That way dry absorbent would always be available for the next dive. While it was tempting to pre-breathe the rigs on the main vessel, this would leave moisture in the loop which would instantly freeze. There had already been a death in the USA when a RB diver left a unit to freeze between dives and did not do a pre-breathe prior to a second immersion. The frozen sofnolime did not function.

The inflatable's we worked from were extremely cramped, Cox, 2 divers, 1 safety diver, 2 bailout tanks, one emergency drop station, O2 kit, cameras and lights, anchor and diver communication unit. Because of the above, the pre-breathe of the rigs was done at the last minute prior to diving.

Once submerged there would be an additional wait period at 6m performing a bubble check and to verify the lime was OK and to allow the LCD plasma in the wrist units to warm up and function properly (cold slows them down and even makes the data disappear).

Back on deck it was essential that the units were stripped quickly and as much moisture removed from the counterlungs and hoses as possible. Mushroom valve checks became more important, several times mine had formed ice crystals which affected the seals. Pre-breathing would melt them. The ice forming also gave Al a problem with his counterlung exhaust valve. It was frozen in a semi sealed state and the unit would not hold a negative. Pre breathing would not help and he had to strip it down.

Batteries suffered badly. A new set lasted 3 days maximum, a 200% reduction in battery life. The 3.6v lithium's in the Secondary displays seemed to fair better. I did not change one on the trip.The oxygen sensors were also affected and at the start of a day needed two calibration runs to get them going. Despite the cold and the cramped conditions, things worked extremely well. There is no way I would have done this on open circuit!