This is a story of two parts….
One part, a thoroughly enjoyable revelation about CCR diving during a series of RedBare CCR test dives, and the other, a delve into what makes the RedBare CCR such a refreshing new / old arrival (we’ll come to that!) on the diving scene.
My journey toward the RedBare CCR began with a conversation about rebreathers in general. I liked the idea of a CCR for my own ambitions and projects, which needed more time, safety and redundancy without carting around excess cylinder loads. However, recognizing that a CCR has more processes to monitor (O2 monitoring and injection, CO2 removal etc.) for these benefits, meant I wanted a system that made CCR diving simple to use, but offered me access to complex information, and chances to resolve dive or unit problems without ending up on open circuit unless absolutely necessary. So… simple and complex all at the same time? How was that going to work?
Rebreathers must do two things to provide us with breathable gas:
Inject O2 and remove CO2. That sounds simple, but then we end up using galvanic O2 cells to monitor the gas, chemistry to remove the CO2, first stages to supply the gas, electronics to make it all work together and then sensors to ensure us that the chemistry is working correctly and thus that the gas afterwards is CO2 free. If all goes well, the numbers need to stack up, and are presented to us in an ‘easy to check’ way. Technical diving means if we need one, then we should take two, so a backup system is needed. Chuck in making sure that we still have enough gas on board, a battery readout and some of that good old fashioned dive data, time and depth – it’s all starting to look a bit like a plane cockpit. But you don’t get a co-pilot or flight engineer – there’s just you. I’m definitely not a fan of using myself as a gas sensor unless the McDonalds reality has hit the fan, so I wanted proper instrumentation.
Let’s start with this conundrum – how can all this be made simple?
The RedBare HUD has an ‘at a glance’ answer – use the computer to compare all these readings to what you asked for. Everything OK – Solid green. Slight issue you can manage? Alternating Blue Green. Imminent dangerous gas – a Flashing Red and a backup buzzer gets your attention. Just for good measure, a white LED gives deco status as stops overhead, at your stop, or too shallow / too fast. OK great – I like simple, but I also like OCD, and I want to verify and double check as and when. Of course, there is plenty more detail on the handsets, especially if you go into the menu’s, but this is the simplest HUD status system available. It really couldn’t be simpler or more intuitive, which is what you want for 99.9% of your dive time.
Monitoring everything also takes us away from the simple ‘gas go round’ rebreather concept and into a proper life support system (LSS) philosophy. The unit does everything it can to keep you alive and well; part of that concept is the early warning system, giving you, the user, the ability to make sensible decisions and course corrections ahead of time. On the RedBare CCR, having a green light doesn’t just mean your PO2 is good, it means that all systems are reporting in happy; it symbolizes a level of system ‘confidence’ to not only continue, but to finish the dive.
But a fancy HUD is nothing without some solid performance to take us on great dives. We need to look at O2 monitoring / injection and CO2 removal. We’ll look at CO2 removal first as everyone loves to chuck durations around in the game of CCR top trumps.
The RedBare has the proven class leading CO2 filter (scrubber, stack, you choose) from the Sentinel at its heart. 2.25kg of Sofnalime delivers the only unit with a 4 hour CE duration under the latest 2013 standard. This fierce test pits harsh loads against the filter, meaning it will last far longer under more benign actual dive conditions. Time to breakthrough in the 40m air diluent test is 140 min, while the 100m trimix DIL test has 47 min to breakthrough. You can ask the others to show you theirs now….
Part of the secret to this performance is the heat generated in the filter by exhaled gas being fed in directly (no exhale counter-lung) and the insulation provided by the returning gas being wrapped around the chemistry.