Rebreather diver dies in 6 feet of water - Cyprus

[AJ]

As you said, whats between your ears can make you safe or unsafe, but it is a confirmed fact that CCR's are MUCH less forgiving than OC, vis a vis more 'dangerous'.

I did not say anything in contrary did I? OC can go wrong as quicly can CCR. However CCR is more complicated so more things can go wrong. That's all I'am saying. Check and double check everything all the time, don't assume anything.

My problem with a lot of divers is they trust computers, diving operators, instructors, buddy's and so on to get home safe. In my mind this is unwise behaviour and you never should trust anyone or anything when it comes to your own safety. Safety to me means you have checked your gasses, equipment, buddy and dive plan. OC or CCR does not matter to me, except with CCR you have to be even more vigilant than OC because of higher complexity.

But does that mean it's more dangerous? That depends on how you define 'danger'.

 

[bumcikaz]

I did not say anything in contrary did I? OC can go wrong as quicly can CCR. However CCR is more complicated so more things can go wrong. That's all I'am saying. Check and double check everything all the time, don't assume anything.

My problem with a lot of divers is they trust computers, diving operators, instructors, buddy's and so on to get home safe. In my mind this is unwise behaviour and you never should trust anyone or anything when it comes to your own safety. Safety to me means you have checked your gasses, equipment, buddy and dive plan. OC or CCR does not matter to me, except with CCR you have to be even more vigilant than OC because of higher complexity.

But does that mean it's more dangerous? That depends on how you define 'danger'.

You do trust same things as well, computer gives your ndl, your instructor certified you and so on
Rebreather is more complex but it not necessarily more dangerous, on 200-300' dive rebreather is safer to me than oc, shallow dives oc is
Po2 drops quick on ascend and harder to maintain it in shallows, but i dont think either one of the systems is more dangerous than other, one is more complex that other thats all
At the end of the day equipment dont kill people, operators errors do

 

[Kay Dee]

AJ, If you would be so kind, would you mind answering the question from my first post, i.e. do you dive OC or CCR?

TIA

By the way, did you bother to read the following? Note the last line (now underlined). Like I said, and not just with this review, a PROVEN fact!

A comment made by GLOC of Andrew Fock's CCR Fatalities Paper - Published and Downloadable [Archive] - The Dive Forum

"Andrew Fock's CCR Fatality paper finally published. The data is not perfect but the best we have

http://www.dhmjournal.com/files/Fock-Rebreather_deaths.pdf

There is no one unit worse than another and the increased risk is somewhere between 4 and 10 times for CCR diving."

 

[lamont]

One claimed advantages of a leaky valve is to act as a backup in this situation.

It isn't though.

You have to turn your O2 off or the valve leaks constantly above water the whole time you are gearing up (and if your valve knob gets bumped in the back of the truck and rolls on a crack it'll drain your whole tank). That means you typically shut down your O2 after you've done most of your gear checks. You then need entry and descent checks to make sure that you turn the thing back on.

That makes the probability that you descend with your O2 off a lot higher.

 

[doctormike]

It isn't though.

You have to turn your O2 off or the valve leaks constantly above water the whole time you are gearing up (and if your valve knob gets bumped in the back of the truck and rolls on a crack it'll drain your whole tank). That means you typically shut down your O2 after you've done most of your gear checks. You then need entry and descent checks to make sure that you turn the thing back on.

That makes the probability that you descend with your O2 off a lot higher.

I see, thanks. Have never used one. Is there a configuration where you can just shut off the leaky valve but still maintain a functioning O2 MAV? So at least you could fly manually if you had left the valve off? Or is the valve incorporated into the MAV?

 

[lamont]

I see, thanks. Have never used one. Is there a configuration where you can just shut off the leaky valve but still maintain a functioning O2 MAV? So at least you could fly manually if you had left the valve off? Or is the valve incorporated into the MAV?

The valve is just a normal valve on a scuba bottle. You could route off board O2 into your MAV or you could come up with some kind of additional in-line valve to shut down the leaky valve. But now you've just added more complexity (and you're even more likely to dive with the MAV on and the leaky-valve off entirely now -- since your MAV failing to work isn't a huge clue that you're not getting any constant flow) and an inline valve is going to either be behind you, or its going to start to complicate your hose routing. I don't see how any of that would help anything rather than just make it worse.

 

[doctormike]

The valve is just a normal valve on a scuba bottle. You could route off board O2 into your MAV or you could come up with some kind of additional in-line valve to shut down the leaky valve. But now you've just added more complexity (and you're even more likely to dive with the MAV on and the leaky-valve off entirely now -- since your MAV failing to work isn't a huge clue that you're not getting any constant flow) and an inline valve is going to either be behind you, or its going to start to complicate your hose routing. I don't see how any of that would help anything rather than just make it worse.

Yeah, I see. I guess as long as you realize why your PO2 is dropping, it would be just as easy to turn on your O2 if you forget to turn it on as it would be to open a flowstop to the valve in the same situation.

 

[ajduplessis]

Yeah, I see. I guess as long as you realize why your PO2 is dropping, it would be just as easy to turn on your O2 if you forget to turn it on as it would be to open a flowstop to the valve in the same situation.

The problem with reduced PO2 is that the diver might already be unable to correct the problem, or bailout.

 

[doctormike]

The problem with reduced PO2 is that the diver might already be unable to correct the problem, or bailout.

Yeah, but you should be aware of that before you get to that point. My instructor drilled one thing into my head, and that was always know your PO2. During training, flying it manually was hard when combined with other skills, but it really forces you to be on top of things.

It seems that looking at hypoxic events, the problem is one of monitoring, not delivery. I have to be very careful of that as a photographer, and I really like the NERD for that reason.

 

[cathal]

It isn't though.

You have to turn your O2 off or the valve leaks constantly above water the whole time you are gearing up (and if your valve knob gets bumped in the back of the truck and rolls on a crack it'll drain your whole tank). That means you typically shut down your O2 after you've done most of your gear checks. You then need entry and descent checks to make sure that you turn the thing back on.
That makes the probability that you descend with your O2 off a lot higher.

I dive a rEvo for the last 5 years and this has never been an issue. The rEvo CMF operates at .8 Litre per minute i.e. simple maths with 600 litres in a typical O2 CCR cylinder it would take 750 minutes (600/.8) to empty the cylinder. Even with the cylinder left on for an hour you would only lose 48 litres of O2. So forgetting to shut of the O2 between dives is not critical.