Quote: (Originally Posted by
Ben Field)
1. First stage- MCCR's require (generally) high but fixed IP, whereas Solenoids require low but balanced IP. Recreational units would be overcomplicated with twin O2 tanks, even H valves and two regs- I think that a Dual IP output reg or similar system is required before this is viable for the majority.
A recreational unit wouldn't need twin O2 tanks or regs. Normally the fixed IP on a manual Rebreather allows depths down to around 100 meters, well outside the recreational boundaries. If one O2 delivery system fails for some reason, it could have failed anyway using either only manual or only electronic control. The only reason for using twin O2 tanks/regs would be redundancy, which is usually not standard on any rig. You check your PO2 now and then and it's always possible to fly manually without any "O2-addition-aid".
I have used a HH-KISS for many years and I like the combined benefits of the two systems, but I've come across people who seem concerned about having two systems and who for some reason think that these systems (technically) would have a higher likelyhood of individual failure when used together?
I have no problem relying on a "parachute" functionality in a stressful situation and if it woulnd't work, then itīs not worse than not having it in the first place. It's like having ABS brakes in your car. They might fail without you noticing it, but if they don't they're still good to have when you need them, and it's not an added problem unless you drive around anticipating that it will save your life one day. Then you need to change your mindset!
I can understand the comment that an electronic system might make you complacent over time, but depending on how you see it you have a manual Rebreather with a "parachute" or an electronic unit with a "battery saver". Anyway, YOU are still responsible for knowing your PO2.