stop or going on ?

Hi All,
after years of home building and rebreather diving for the first time of my life I am wondering : what should I do ?
should I go on diving rebreathers or should I stop ?
the recent deaths on mccr's make me think that what I was sure to be safe is not....
2 week ago I was at 30m , my 3 sensor were reading 1,00 and I started injecting o2 in the loop...the ppo2 did not jumped...
as a stupid h...le then I am I injected again...and again ...no result....i went up a little bit and suddently my buzzer started to shout....2,5 bars....
it means that 10m below my ppo2 must have gone up to at least 3.5 !!!!
the 3 sensors where reading the same...(humidity on the membrane ?), the three sensors just went up to 1,05 after 3 o2 injections .....
why have I been so stupid after years of ccr kiss diving...?
how come one can inject 3 time with nearly no ppo2 raise on the display ?
how come the 3 sensors can give the same bad reading at the same time ?
my religious belief that 3 roughly equal ppo2 datas is the thuth have gone away for ever....
soes
does it means that we always have to be perfect machione to interpret oxymeters and sensor data to be able to survive underwater ?
is there any room for error ?
I don't know what to think about all of that ...even if kiss syle seem safe, i don't feel confortable anymore...
regards

jean mi

jean mi, I suppose your 3 read-outs are independant???

did not see you latest development, so...

what cells are you using? from the same batch, same age??

regards
paul

Hi Jean,

Firstly I don't know anything about your homebuild CCR other than you allude to it being KISS style MCCR.

The first thing that strikes me from your email is that you may have uncovered a bug in the design of your homebuild- no slight intended, exactly where and how are your sensors located? (If you believe wet cells rather than age or batteries or corroded cables are not to blame?)


well, I dived a dolphin bassed ccr kiss style rebreather, really classicly designed, o2 injection in the canister, hydrogom valve, sensors locaed in the inhalation side, in a tecme cell holder, the electronics are classic 2, it is based on a pic 16F876 , nothing special...
I dsplay the battery voltage (6 volts when I had the problem), I was just using a crap lumberg connector when it happend and had faced a couple of sensor signal losses in the 3 previous dives, I had tried to fix the problem in vain changing the connectors.
I've got rid of the connector now....last week I did not have the problem anymore....but ....I've been thinking back to the human problem and it really make me wonder if ccr kiss is not mutch more dangerous then that I've thought formany years....

Secondly you state "the recent deaths on mccr's make me think that what I was sure to be safe is not"
Perhaps it has been lost in translation but I am pretty sure you never thought diving, let alone on a Rebreather was sure to be safe?

i did not get it , what do you mean ? sorry for my poor english

Which MCCR accidents are you referring to, is there anymore data? As Alex's accident invesitgations have shown there are many causes for deaths on Rebreather's, not all of them the fault of the unit.


I have no info at all except that it was a mccr style rebreather and a good diver that passed away....I tought that only stupid undiligent divers could die....verybody canmake an error and the price is...expensive.



Last of all- the choice to add more O2 in the light of questionable sensors, this was probably instinctive as your desire was for the PPO2 to rise,

this the very problem you are rigth, I don't mind the connexion proble I don't mind the technical problem, I've hardly fall in the trap , and I need to understand that not to fall in.
I remembers the numérous posts of pyle in the newdesign list saying that rebreather were tricky willers waiting for you low down your gaurd or commint the fault to kill you...


however I get the impression alot of divers get PPO2 obsessed, trying to maintain setpoint.

you are probalbly rigth but in my case this day it was really not the case, I really don't mind the set point , I tune my hse on 1,2 and dive the Rebreather from 1,1 to 1,3 without worrying if it get's down to .90 or so on my way up...I've got a respectable experience ...it is the problem....it is worst...

You wanted it to go up- so you kept trying, whereas in hindsight perhaps you could have checked them first?

yes I was totaly wrong...but who is not on day or later....

I don't know if its good or right or wise but at depth if ever I have a question in my mind with regard the sensors (on both Displays, Shearwater & HUD) I typically add DIL first, maybe not a flush but on the dives I do this will always generate a rapid change in the readings (downward) So- I know the sensors are responsive and I know the loop is breathable (if it was too high its now lower/safer and I don't dive lean mixes so it won't be too low.)

well thing are even worst then that you think, if I ever had failed to flush and checked the sensors it would have oly mean that the guy (me) is stupid and that I woud have been the only responsible for what happened, but it is not the case....when I arrive from arround 45m to 30m I flushed my circuit and had a look to my triple display : 0.60 bars with a dil of 15% O2 it was perfect....then I started injecting....it went up to 1.00 with a good hard injection...and it stopped climbbing after the second good big injection...the third did not changed anything.......
it means that a the sensors have been totaly correct after the flush at .6 and unable to climb up to 1,2 where I wanted my mix to go....(the sensor or the circuit).
It means that everything can happend even thing that one can't read in any training book of learn from any agency....
3 sensors ok together 0.6 and one minute later the 3 seneors stucked at 1.00 but all equal and one minute later the three sensors up to 2,5 bars without additionnal injection of course....whouaw !!!
you see the kind of what if we have to plan to stay on the safe side ????

Maybe all this is just a warning, maybe unwittingly you slipped into alittle complacency,

definitly yes, it is always the problem...

I'd say that the fact you wrote that mail was a good thing, you can use your new found suspicion to check your design and refresh your skills.

speking of problem is more then necessary , Ive always done it just to go ahead....

Just in my Very humble opinion, Best of luck & Dive Safe,
BEN

I know we all sometimes get too fixated on our gauges & believing what they say, so it's easy to second guess here, but if I kept injecting O2 with no change to the sensor reading and particularly after reading through your post, hopefully I'd figure that something is wrong somewhere in the loop and bail out.

Doesn't really matter if it's sensor failure or another failure.... Get off the loop. I believe too much stock is put into "Staying on the loop." No data to support this but it's a gut feel that some of the Rebreather fatalities came from divers mindset of staying on the loop. There is no shame in bailing out and living to dive another day.

As to whether or not you you should give up Rebreather dives.... Only you can decide that one.

Richie

jean, keep diving! that is if you can handle that there is some risk assumed no matter what type of rig you dive or how vigilant you are. I don't know of the incident you speak of. So far I've heard of one death on an mCCR. The idea that there won't be more is absurd. There are more and more mCCR's coming out and the number of people diving them must be increasing significantly. As much as they foster responsible habits, there are still bound to be mistakes or sudden illness. We should expect that every so often there is going to be a fatality on them. In fact, ironically, there could be a rebound effect that the low fatality rate fosters, luring people to be more complacent or attracting people who are not as attentive. There is still so much to learn from the near zero fatality stats on mCCR's, hopefully Alex can help us out there.

g

Hi paul,

perfect sensors...I suspect the lumberg connector to have oxidize and ****ed the common ground...
don(t know what to think about all of it...

jean mi