@Dan_P if you seriously think the decompression profiles that AG advocates are safer *which is literally not actually an algorithm but an essentially random just add deep stops in as you feel like it*, then you have far more serious things to worry about with your diving than the z-system. Following their deco profile is far more likely to land you in the hospital than the Z-system based on the results of that study.
UTD Ratio deco discussion
here is a 34 page discussion on their ratio deco with weigh ins from some seriously prominent people in decompression studies *including many who were previous believers in deep stops* and not a single one can find any reasonable justification for UTD ratio deco and they all said that it was pretty much unsafe.
UTD Decompression profile study results published
and a 30 page discussion on the same. Conclusion is that RD is more dangerous than 30/85 which very few are advocating instead pushing for the GF-lo to be much higher.
Seriously, if you truly believe in RD, then don't expect me to ever complete a decompression dive with you as a "team". I may consider waiting for you at the 10ft stops, but I'll be leaving you quite quickly once we hit the deco stops which I suspect will be the discussion from any sane person who wants to avoid DCS...
On the Z-system. No study can be completed without putting people in serious danger.
To evaluate it is simple, no class required, no in depth scientific study required, just 6 questions for me that say enough.
Question 1. Does the system solve the problem that it was designed to solve:
Yes, it allows you to have a system that always allows you to donate a long hose regulator from your mouth to an OOA diver
Question 2. Does the system follow the DIR principal of KISS-
Resounding no. Many extra o-rings, extra hoses, funky connectors with a second adapter from NPT to reg *literally no idea why they didn't use Omni Swivel BOV QD's which are half the price, work just as well, are significantly smaller, and are less complex since they connect straight to reg hoses*, no ability for other divers to breathe from stage tanks due to lack of second stage attached to the bottle, a manifold system behind your back that you can't see, an extra valve knob for isolation, and non-standard hose lengths due to manifold location.
Question 3: Is the cost of such system justified-
at $1k minimum I don't think so
Question 4: does the system follow the principals that UTD was founded on-
Unify: it unifies the two options for open circuit diving to a primary donate paradigm
Consistent: within open circuit the OOA scenarios are consistent. It is not consistent with decompression/stage bottle use compared to manifolded doubles, nor is the general use consistent with manifolded doubles. It may be consistent with rebreather usage if the QD's are all QC6.
Scalable-within open circuit it is scalable, but it is not compatible with CCR due to the loop restricting primary donate
Interchangeable-it is interchangeable from an OOA scenario, but it does not allow the bottles to interchange with those used in standard backmount doubles configurations for deco or stage use due to lack of second stage on the bottle. Every diver would have to carry a spare second stage on a QC6 and for a bottle switch actually disconnect their second stage and plug it into another bottle if the manifold fails. That is a recipe for disaster in a cave.
Question 5: Have there been any accidents that could have been prevented with such a system? BSAC certainly would argue that secondary take prevents more accidents than primary donate so they're obviously in the opposite camp. The vast majority of the agencies don't agree to the point of not requiring any one standardized regulator configuration and leave it up to the instructor
Question 5: Is the complexity warranted and does it make sense? I.e. is this a system looking for a problem. I certainly think so.
My opinion? AG thought that it was great on paper and figured he could make a boat load of money and inflate his ego. No different than his self absorbed view as a scuba savior for decompression and that he knows better than all of the actual decompression experts and doctors with a business degree... Just my opinion. No different than charging $550 for regs made in Taiwan *that's more than Halcyon who is actually selling regs made by Scubapro*. No different than charging $1100 for lights that have 10 year old technology in them. etc etc etc
