CCR "Myths"

Ben Field

Ben Field

All IMVHO obviously...
No offence to Randy but none of his "Myths" seem particularly mythical to me- more like example of bad instruction in general than CCR or even diving specific?

How about some real Myths of Rebreathers, here is a few to get you started-

1. Know your PPO2
(Controversial but it is largely irrelevant unless you remember what is was and can guesstimate what it might be next time you look- otherwise its just the Single point calibration debate all over again :-) Irrespective of rebreather type IMO

2. Rebreathers are better because- Constant PPO2
(Nonsense, they are better because they can create the Right PPO2 for the given point of the dive, it doesn't have to be constant to achieve that)

3. Bailing out onto the same decompression plan for CCR
(The GF's or settings chosen for a CCR ascent are rarely suitable for an OC ascent, MTFU- make proper tables and bailout properly, get up, get deco'd and get out)

4. Look at my sexy configuration from the Internet!
(News Flash- What works on a team dive in a clear Florida cavern is largely unsuitable to a silt out wreck dive with a buddy off slacks at the bottom of the English Channel)


Feel free to add or debate :-)
 
Ben,

My take on the various myths is not some much if you agree with them or not but that we consider them exactly as you have proposed in your post. Specifically as it applies to Randy, he is making some points that may or may not be seen as politically correct by training agencies etc. I see value in the discussions created by his and your post here regardless if you are a truly seasoned CCR diver or if your a newbie in the CCR ranks. The more that we can get people to "think" and make planned purposeful decisions the better.

I think the points that you raised are all good ones. It will be interesting to see if any of the are in Randy's list as he shares the rest or if they are a few that should be added.

Dive Safe

Mark
 
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Ben,

Very good and interesting points, and certainly worthy of discussion. I'm going to finish posting my Myths first before I come back and comment on yours so that I don't get sidetracked. I do like your list! :)

Regards,
Randy

Ben Field said:
No offence to Randy but none of his "Myths" seem particularly mythical to me- more like example of bad instruction in general than CCR or even diving specific?

How about some real Myths of Rebreathers, here is a few to get you started-

1. Know your PPO2
(Controversial but it is largely irrelevant unless you remember what is was and can guesstimate what it might be next time you look- otherwise its just the Single point calibration debate all over again :-) Irrespective of rebreather type IMO

2. Rebreathers are better because- Constant PPO2
(Nonsense, they are better because they can create the Right PPO2 for the given point of the dive, it doesn't have to be constant to achieve that)

3. Bailing out onto the same decompression plan for CCR
(The GF's or settings chosen for a CCR ascent are rarely suitable for an OC ascent, MTFU- make proper tables and bailout properly, get up, get deco'd and get out)

4. Look at my sexy configuration from the Internet!
(News Flash- What works on a team dive in a clear Florida cavern is largely unsuitable to a silt out wreck dive with a buddy off slacks at the bottom of the English Channel)


Feel free to add or debate :-)
Click to expand...
 
Ben Field said:
No offence to Randy but none of his "Myths" seem particularly mythical to me- more like example of bad instruction in general than CCR or even diving specific?

How about some real Myths of Rebreathers, here is a few to get you started-


1. Know your PPO2
(Controversial but it is largely irrelevant unless you remember what is was and can guesstimate what it might be next time you look- otherwise its just the Single point calibration debate all over again :-) Irrespective of rebreather type IMO

2. Rebreathers are better because- Constant PPO2
(Nonsense, they are better because they can create the Right PPO2 for the given point of the dive, it doesn't have to be constant to achieve that)

3. Bailing out onto the same decompression plan for CCR
(The GF's or settings chosen for a CCR ascent are rarely suitable for an OC ascent, MTFU- make proper tables and bailout properly, get up, get deco'd and get out)

4. Look at my sexy configuration from the Internet!
(News Flash- What works on a team dive in a clear Florida cavern is largely unsuitable to a silt out wreck dive with a buddy off slacks at the bottom of the English Channel)


Feel free to add or debate :-)
Click to expand...

Ben number 2 on your list ,
I used to have this problem when I was oc diving with ccr guys thay used to think I'd need a shit load more deco cos I was not on a 1.3 set point , Lol I'd take my O2 dose at 12m and then 6m and I'd be out be4 them ,
 
I think the "Know your PO2" is intended to mean "Know within a decimal point or so of your actual PO2" and not "Know your exact PO2 at all times during the dive".

That being said, I have found myself distracted by something "shiny!!!" underwater and didn't pay attention until I was upwards of 1.9 and all 3 cells were blinking red. That to me is the kind of situation the statement is trying to avoid, not that you know you're at 1.12, 1.15, and 1.10 on your cells.

I also think it is especially important to keep that statement in mind on mCCR, since a lapse in attention can quickly turn into a situation where you're not in a good spot.

YMMV, this is just my take on it. Personally, every time I look at my computer and my PO2 isn't where it should be, Doug's voice comes into my head and says "Always know your PO2!!"
 
hroark2112 said:
until I was upwards of 1.9 and all 3 cells were blinking red.
Click to expand...

How did that happen?

1. Faulty cells
2. Faulty electronics
3. Rapid descent spiking the cells
4. Inadvertent human interaction
5. None of the above

Seems odd for all three to suddenly go high unless...







Sent from my ivory tower using Tapatalk
 
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GaryL said:
How did that happen?

1. Faulty cells
2. Faulty electronics
3. Rapid descent spiking the cells
4. Inadvertent human interaction
5. None of the above

Seems odd for all three to suddenly go high unless...





Sent from my ivory tower using Tapatalk
Click to expand...

#4. Inadvertent human interaction.

The above is priceless.

Examples are Accidental oxygen flush or forgetting to adjust your setpoint/ changing to an unwanted setpoint.

I've seen or heard about both situations. The one situation required a bailout and the other created a long deco for the diver.

Don't be inadvertent. Be purposeful.


Sent from my iPhone using Tapatalk
 
Garth said:
Examples are Accidental oxygen flush or forgetting to adjust your setpoint/ changing to an unwanted setpoint.

I've seen or heard about both situations. The one situation required a bailout and the other created a long deco for the diver.
Click to expand...

Forgetting to adjust the setpoint for the whole bloody dive? Someone should just go back to OC
 
rjack said:
Forgetting to adjust the setpoint for the whole bloody dive? Someone should just go back to OC
Click to expand...

I think someone posted a good thread on doing his 80m dive on low set point ,
Think he spotted his problem be4 he left bottom and run 1.5 sp back to 6m then O2 deco
Seemed to work ok and not to much more deco than his would have done if he had changed set point when he should have ,

Think it was MAtt that posted , my be on rbw if not here,
 
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Mr fish said:
I think someone posted a good thread on doing his 80m dive on low set point ,
Think he spotted him problem be4 he left bottom and run 1.5 sp back to 6m then O2 deco
Seemed to work ok and not to much more deco than his would have done if he had changed set point when he should have ,

Think it was MAtt that posted , my be on rbw if not here,
Click to expand...

Ok but my HUD would have been screaming at me the whole time. Seems like a pretty big lapse.
 
And if your HUD hadn't been screaming at you? Would you have remembered EVERY dive?

I kinda like having auto-switch on my rig but it's a double edged sword like just about every other engineering solution. Because it just takes care of it, setpoint management seems to be one of those things I no longer pay much attention to.
 
statements like 'someone should just go back to OC' just encourage people not to post cautionary tales for others to learn from lest the smartarses take the piss. maybe it's just my perception but it seems to be a cultural thing as most of the 'anybody who makes a mistake is an idiot' brigade seem to live in the land of big hats and jangling spurs.

we all have lapses, and the more dives you do the more chances you get to screw things up. some mistakes are a big deal, most aren't, but anyone who takes the piss out of people who hold their hand up for the education of others and think they never personally make mistakes is fooling nobody but themselves.
 
rjack said:
Ok but my HUD would have been screaming at me the whole time. Seems like a pretty big lapse.
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Don't think Matt had a hud at the time , I could be talking shite about whan he did notice he was still on low set point ,

I remember it as he pulled it all back by using his ppo2 to get the same avg O2 he would have if he had run 1.3 all the dive ,
It was deep but I can't remember how long he was on low set point for ,

It was a good post and it stuck with me ,
 
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Mike Ferguson said:
statements like 'someone should just go back to OC' just encourage people not to post cautionary tales for others to learn from lest the smartarses take the piss. maybe it's just my perception but it seems to be a cultural thing as most of the 'anybody who makes a mistake is an idiot' brigade seem to live in the land of big hats and jangling spurs.

we all have lapses, and the more dives you do the more chances you get to screw things up. some mistakes are a big deal, most aren't, but anyone who takes the piss out of people who hold their hand up for the education of others and think they never personally make mistakes is fooling nobody but themselves.
Click to expand...

No check on ppO2 the whole bottom time of the dive seems like a pretty big oversight to me. Sure 80m was probably short, I get that.

I have no spurs.
 
I once forgot to change the setpoint on my stand alone constant PO2 computer. Since it was a backup I wasn't checking it very often. I felt like an idiot but not bad enough to go back to OC. :-)


Sent from my iPhone using Tapatalk
 
Ben Field said:
1. Know your PPO2
(Controversial but it is largely irrelevant unless you remember what is was and can guesstimate what it might be next time you look- otherwise its just the Single point calibration debate all over again :-) Irrespective of rebreather type IMO
Click to expand...
I might be misunderstanding your comment, please forgive me if I am but I keep re-reading it and I can't get past the "largely irrelevant".

If we manufacturers and early users of CCR haven't got across the importance of looking at your handset so that you know what you're breathing is close to what you want it to be for life support or deco - then clearly we have failed miserably.

We used "Know your PO2" because that's what Richard Pyle dubbed it in his early rebreather survival articles. Maybe we should have just written and ensure instructors state: "Look at the f*cking handset".
 
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Martin Parker said:
I might be misunderstanding your comment, please forgive me if I am but I keep re-reading it and I can't get past the "largely irrelevant".

If we manufacturers and early users of CCR haven't got across the importance of looking at your handset so that you know what you're breathing is close to what you want it to be for life support or deco - then clearly we have failed miserably.

We used "Know your PO2" because that's what Richard Pyle dubbed it in his early rebreather survival articles. Maybe we should have just written and ensure instructors state: "Look at the f*cking handset".
Click to expand...

I was trying to differentiate between- "Looking at the current PPO2" and "KNOWING your PPO2" which requires memory of what it was and understanding of where it will go and why.

IMO A-LOT of rebreather divers Only "Look" so only know (if you're lucky) their current PPO2, which IMVHO is irrelevant- perhaps Instructors should periodically cover the handset and then ask- "what was/is/will be your PPO2?"

Personally I think "Look at the F*cking handset" is the bare minimum Instructors should be saying! :-)
Better still a pointy stick to jab divers in the eye periodically unless they look and read their handsets would be better!

Know your PPO2 is abit of a Steady Green to me... if it doesn't change how do you know it isn't stuck? So the depth/activity/dilution influence on the loop contents that keeps it moving should keep people on their toes- as long as they track the motion of their PPO2.
Perhaps ECCR's should artificially wobble the PPO2 a bit?
 
Now I get it, Ben.

If the breather is telling you 1.3 then all you know is that the breather has driven the loop to what it thinks is 1.3. Without a "calibration" flush of dil or O2 you really don't know for sure what's in there.

Still, reading the handsets is a good start and you'd be having a God-awful day if three cells agreed on the wrong value to lead you into a false sense of security.
 
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