My first (and unpleasant) rebreather experience

[Jax]

I think HowardE is just pointing out that the low setpoint was not part of the reason why I was experiencing these problems. That said, I find the discussion around the setpoint interesting as well. Serves as another reminder that you just don't know what you don't know - until you get a CO2 hit and ask around on ScubaBoard, when it becomes clear that you really didn't know squat

At any rate, thanks for all the responses. I hear what you're saying about this dive being a bad idea and all but I'd have to add that it was ultimately my choice to do the dive and to continue with the dive when things didn't feel right. Ultimately, safety is the responsibility of the diver, not the instructor or DM or boat captain. I won't be diving CCR any time soon (if ever) but hopefully this experience will have reminded me to abort any dive where I'm not comfortable.

So, is it that this dive (try-it dive) was a bad idea?

Or is it that this particular rendition of a try-it dive was not good?

In other words, if such an opportunity knocked (and I am in D_B's camp on this), is it a bad idea to do a demo dive if you are not a tec diver?

 

[TechBlue]

So, is it that this dive (try-it dive) was a bad idea?

Or is it that this particular rendition of a try-it dive was not good?

In other words, if such an opportunity knocked (and I am in D_B's camp on this), is it a bad idea to do a demo dive if you are not a tec diver?

I think deefstes was very generous in assuming the responsibility here and we'll leave that alone.

Why would you need to be a tec diver to take a try dive on a rebreather?
When you put any "student" in the water with new equipment that they may not be familiar with, standards, procedures and safety measures need to be followed to ensure the safety of the divers and in this particular dive with the information given they were clearly ignored.

So in answer to your question I would say (b)

 

[TSandM]

I think, before anybody tries any equipment at all, they should have a basic idea of how it works and how to troubleshoot it. Before I did my rebreather "try dive", I had watched someone taking his full training on the unit for the better part of a week. I hadn't sat through ALL the lecture time or the pre-dive stuff; I couldn't have put the device together myself or anything like that. But I knew what the parts were and how they were expected to work, and what the displays were and what they would tell me. I also knew enough about rebreathers in general to know what the issues are. I think, had I been in Deefstes' place, I would have known enough to know something was wrong with the unit and bail, before getting in the water, although I can't be sure of that.

But I don't think a rebreather is like a backplate . . . I don't think you can say to somebody, "Here let me strap you into this thing, and let's go diving."

 

[Jax]

I think, before anybody tries any equipment at all, they should have a basic idea of how it works and how to troubleshoot it. Before I did my rebreather "try dive", I had watched someone taking his full training on the unit for the better part of a week. I hadn't sat through ALL the lecture time or the pre-dive stuff; I couldn't have put the device together myself or anything like that. But I knew what the parts were and how they were expected to work, and what the displays were and what they would tell me. I also knew enough about rebreathers in general to know what the issues are. I think, had I been in Deefstes' place, I would have known enough to know something was wrong with the unit and bail, before getting in the water, although I can't be sure of that.

But I don't think a rebreather is like a backplate . . . I don't think you can say to somebody, "Here let me strap you into this thing, and let's go diving."

That sounds very wise - as always!

However, were I to ever be around such an opportunity, it is more likely that I am attending some business function at some oceanside city. Therefore, I would not have the opportunity to listen in on a class, nor would I have any gear familiar to me. Given my lack of experience in general, this sounds like an experience to be regretfully declined. . . .

 

[TechBlue]

That sounds very wise - as always!

However, were I to ever be around such an opportunity, it is more likely that I am attending some business function at some oceanside city. Therefore, I would not have the opportunity to listen in on a class, nor would I have any gear familiar to me. Given my lack of experience in general, this sounds like an experience to be regretfully declined. . . .

Caution is always wise, breather diving is not for everybody But never say never

 

[Jax]

Caution is always wise, breather diving is not for everybody But never say never

You're right on that!

The problem is, I like to try everything at least once . . .

 

[Cave Diver]

So, is it that this dive (try-it dive) was a bad idea?

Or is it that this particular rendition of a try-it dive was not good?

In other words, if such an opportunity knocked (and I am in D_B's camp on this), is it a bad idea to do a demo dive if you are not a tec diver?

Wow, interesting thread. I'll come back to some of the other things when I've got more time (although they've been pretty thoroughly covered already).

It seems like there were issues with this trial. I did a CCR try me dive prior to switching. There were several of us in the water trying units at one time and the instructor was supervising above. Each person in the water had another very qualified CCR diver as a "buddy" who was monitoring their PO2 and keeping an eye on them for the entire dive.

IMO, an inexperienced person should NEVER be alone or with no in water supervision on CCR.

 

[TechBlue]

I just pulled this from a thread on decostop these guys received bad information during their training from their instructor, deefste I believe this is what you experienced during your try dive.

CO2: The rebreather incident

 

[Gill Envy]

It's possible but unlikely that the scrubber was spent and you were experiencing co2 build up in the loop.

I think those who mentioned loop volume are more likely onto it. you could have either exceeded the ideal loop volume or had too little...

-did you have "chipmunk cheeks" with a sense that the mouth piece wanted to burst from your mouth? or
-were you struggling to inhale deeply enough?

Either of the above scenarios can lead to Co2 build up in your blood, where you are not exhaling deeply enough to off gas Co2, which as it builds causes all kinds of biological alarms to go off in your system like giving you a sense of panic, hyperventilation and a general sense of alienation/hyper-vigilance... everything starts to feel weird.

the trouble with rebreather try outs and even "discover scuba" is that folks don't get a thorough introduction and eased into the process... you can walk away never wanting to try it again vs loving it and wanting to do nothing else.

I'd recommend giving it another try and having someone take more time with you in the future... tell them point blank that you had a bad experience the last and have them help you adjust the counter lung volume so that you are comfortable. While being on the loop feels different from taking air from a regulator (on the loop your lungs are doing the work of circulating the air vs a regulator assists inhalation as the air is pressurized) it really should feel generally easy to breath.

my 2 cents,
g

 

[TechBlue]

I wouldn't be able to say but I know it has been a lot. My try-out dive was scheduled for 20:30 and they've basically been doing it since 11:00. From what I understand, the unit would have been in almost constant use (by noobs like me) for most of the day.

Gil,

If they had been using the same scrubber all day long it more than likely was CO2 breakthrough, which would lead to the hyperventilation etc. After going back through the posts I recall deefste also said that he felt short of breath during his one minute prebreath.

Chris