Passive Scr Superiority?

bjornaow

My 5 cent is that a PASCR is safer and simpler but that from one who only read about it and see how my friends Rebreather's goes bust sometimes.

Best regards

Björn

Dutchy

And this is where we all go wrong... We focus on the Rebreather not on the dive. An RB is inherantly more prone to become defective as it shares the same parts that OC has plus it has a few more that can become defective too... All true BUT does that make a dive less safe? Not necessarily... If you get caught in a net or lost in a wreck then what would you rather have? OC or Rebreather? My bet is that you're better of with a RB...
Too much focus in the recurring safety discussions might be on the Rebreather not on the TOTAL risk per dive...but hey that is just my 0.02 cents in a hijacked thread...

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Depth-junkie

Spot on in my book.

ATB
Gareth

Gill Envy

this list needs to be updated, something i saved from another thread a while back, it's a start, maybe others can update the numbers? oh, and it does not destinguish between vision and classic electronics for AP.

Cis lunar MK4/5 - 3 (could be more)
Meg - 8
Prism - 1
Inspo/Evo - about 30 (33-35?)
CCR1000/ Mk15 - 1
SMI 1600 / Mk15.5- 2 )
Kiss (classic) - 0
Kiss Sport - 0 as above
Rebreather-80 - 1 at least
EDO-04 and other clones- 1 at least
Halcyon fridge - 1
Ouroboros - 0

Trying to draw conclusions about safety from such small numbers is pretty much impossible and certainly considering that the total number of hours underwater per unit would be difficult to ascertain and the fact that some, like the meg in particular are more common for rather extreme depths and long dives...but it is worth looking at the fatality numbers anyway...IMHO

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Gill Envy

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Marc T

Though we were speaking about pSCR and THAT was an interesting way to try to understand what is secure and what is not.
Everybody can understand that the ability of staying alive longer in the water can improve your security in case of a problem.
BUT the problem IS does some Rebreather kill you more freequently than other.
The intuitive response is YES AND the numbers are speaking in the same way.
The problem is how to built more secure Rebreather.
SO the INITIAL question of pSCR was a real good one, that was indirectly asking to who know ( because they hown or howned a p SCR ) if its really a secure way with few issues.
A good way is certainly to collect all the real issues on Rebreather of different sort to avoïd fighting again and again against ghosts or fantasms.
Hope will be able in a near future to built efficient Rebreather who are not killing friends or me by surprise.
SO are the pSCR safe: YES and the next step is WHY

Cheers

Marc

Dutchy

Your reasoning is too fast by my taste. Yes it is a known fact that some rebreathers are more often involved in incidents than others (irrespective ofwhether attributable to the Rebreather or not)
Now try compensating for the numbers in use. (There are a few more Inspirations around than e.g. Borisses) Now try compensating for the type of dives these machines are used for. (E.g. compare typical Dolphin dive with a typical Meg dive)..
Can you? I can't which is why I can't tell which one is safer. I can only guess. What I can tell you is that I don't rely on it to work which is why I have a BOV AND bailout.
Hmmmmmm could that be the key to safety? We simply don't know which is why I have a problem with firm statements.... (although they are excelent to start discussion of course )

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Marc T

Saying that an incident is due to the type of the dive is a pure fantasm, most of accident occure in shallow water that has been discussed on a previous thread here.
Concerning BOV its just an evident solution for hypercapnia, so its possible to bail out even if you are breathless and unable to hold apnea.
Can you imagine that you let your Rebreather kill you, no I guess the problem(s) who kill most of RB diver occured so fast that even dont understand what happen or understand the wrong wayr or understand correctly but correct the wrong way.

Dutchy

I think we agree on that. I asked a few questions, I didn't claim to have all the answers. Even the BOV question was answered with a "I don't know". On a sidenote I think a BOV is more than that. It's also a quick solution for lowering ppO2 when a hit is expected or a flood... It buys you time from many (not all) problems.

Until we have all the cards on the table I have problems with firm statements that's all and I can only speak for myself when I say that I don't want to rely on a computer that has been poorly tested to my standards (I've been a Test Engineer for software in medical applications ). I appreciate the efforts that suppliers make, but I can't vouch for their expertise nor budget. Alternatively I could draw my conclusions from Rebreather attributable incident rates but I'm afraid that the installed base is still too small to draw reliable conclusions.

All I have left is personal choice and common sense which led me to beleive that you have to fly a unit manually. (Although I now "beleive" that flying a unit manually a bit above setpoint might be a very valid alternative under certain circumstances)

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Faceless

pSCR is no better than KISS as it's too prone to user errors, especially on open water. Lose control over your buoyancy especially in shallow water and you're dead, forget to switch mixes at sertain depth while accomplishing descent/ascent and you're dead again.
I.e. any rebreather regardless of it's construction and way of flying MUST tolerate at least one worst case failure. pSCR like KISS does not.
Saying that, i think that best solution so far is to fly eSCR in manual mode having electronics watching over you like a "safety net", i.e. electronics may come handy to correct or "put a quick fix on" situation underwater, especially under stress, where taskloading jumps to sky and IQ drops off.

Alex and O.R. team have written excellent document Rebreather Fault Modes :
http://www.deeplife.co.uk/or_files/F...lts_060807.pdf

Now try to read it and apply failure modes described there to pSCR.

Marc T

[quote=Dutchy;73130]incident rates but I'm afraid that the installed base is still too small to draw reliable conclusions.

quote]

I think whe have the database of incident or near accident but most of us dont use it or use it the wrong way for different reasons.
Thats a shame reading so many electric or electronic bugs or usors error with electronic and for only usual response a long discussion on what to do if....
So many of us are diving without a perfect knowledge of their perhaps too complex too and without a real knowledge of what cause death in Rebreather dive.
Some very experienced divers died too, even in shallow water.
Nobody really trust in his Rebreather ( if yes so why bailout ?).
But you also know that most of the death havent been avoided by OC bailout.
So whe are playing with our own lives, somes know over dont know and more dont want to know.