Know your PCO2 (Why Rebreather have no CO2 sensor)

DarkSideOfTheMoon

Disclaimer: I am not a technical diver but I have some basic training OC, in addition I have a PhD in engineering.

Ok guys, I read a lot about Rebreather and how it works and I know about how deco vs gas mix works and tox and so forth and how equipment can fail. So I am just talking out of my ass right now.

What I have to say is that until you have some kind of measurement of CO2 in you loop, you are a disaster waiting to happen. You fly your Rebreather, checking
just your PO2 and injecting whatever dilutant fits your depth. This might be Ok for someone completely a rest, but as soon as you start some kind of physical activity you are at risk (ref Dave Shaw).

I beg everyone of you to write to all manufacturers and donate to researchers that might be willling to put some efforts into a reliable CO2
measurement apparatus.

Also, after analysis as an engineer, if something seems funny with you equip
you just bailout OC and even more, don't dive with it until you understand fully what happened. Sorry for the rant.

Oh and by the way, I believe that in 10-20 years from now we will only see Rebreather. Of course, they will have a C02 monitor by then and everyone will remember you like the ones who "walked on the moon".

Ferg3333

It is my belief that one is already in production or at least testing with ccrb. The effects of hypercapnia are obvious, and sufficent steps may be taken to avoid it, sensible use of scrubber fills and bov's. Says the rebreather diver doing a Phd in Engineering. People know and understand the risks, and diving is all about doing what you are comfortable with, if people were not happy with the calculated risks then there would be no mass Rebreather market.

acanthaster

You seem to be worried about scrubber duration, yet you provided an ultra-extreme example where the concept of "dynamic breakthrough" may have come into play.

TR300

Hi,

I have tested a prototyp of CO2 sensor. It was only at dry land not in water and not at deep.I tested it in rest and under heavy load. All I have learned was, that a rebreather (for sports diver) isn't a system to fight against current or have heavy workload. But this is was I tell all my students. The other thing is what can I do when the CO2 rises ?
ok first STOP (any load), then THINK (what I have to do next) then DO it. (this we learned allready at the OWD). OK when I have a CO2 sensor I can wait until the CO2 falls (after some minutes) then I can be at the loop, slowly ascent and look at my sensors. If the CO2 doesn't fall I have to bailout.
One more interessting questing will be how many incidents in the past where about a hight CO2 ? Are all the "heard attack" incidents going on a hight CO2 ?

Holger

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carcharodon1957

Hi,
Just a small contribution (a light one)
Sorry for my english....

Many training and many exercices are made just with calculation and probability, without lots of true and established bases!

As for example a simple deco calc witch is always made from test,calculation and not usable for everybody(even if its real safe)!

In the army, close cicruit diving protocols are also based on test and guys who pass not threw long diving time in many conditions are not allowed to continue training and getting badge!!

But, from thousand and thousand of dives with CC , single or mixed gaz, there is a few accident because CO2 hits!

So I believe that we can continue to dive without additional control!
A man on the top of the Everest mountain knows his body and metabolism, don't need any gauge to balance o2 and co2!

You should you also know about your metabolism, and there is one solution for it!
Think about it (but a little less and) DIVE more often...........................

BEST REGARDS
Bernard

PhilSiswick

Well said that man!

I'd like to have a CO2 sensor and will certainly get one when they become available on the market. I'm by nature a cautious person and I have dependents - I didn't make the move into Rebreather until I was pretty sure the risks were manageable.

Dave Shaw's incident is an extreme one - similar, I'd suggest, to stating that a Space Shuttle incident is a reason to reconsider transatlantic air travel. You can draw conclusions for future development of the technology and it's applicability to mass usage, but not much more.

For the vast majority of us, with a bit of thinking, preparation and a willingness to sacrifice the objective when things go a little pear shaped before or during the dive, we'll be fine, just as we were on OC.

Cheers,

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I have always felt that the dive I am on is not nearly important as the dives I plan to be on the rest of my life. Tom Rose, 2007

The person who gets the farthest is generally the one who is willing to do and dare. The sure thing boat never gets far from shore. Charles A. Lindbergh

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Ivon

Now that is interesting, does anyone have any more info?

CharlieT

Ivon

There have been previous posts which I think referred to an infra red device for CO2 measurement.

Such a device will arrive but how soon and how effective it will initially be, who knows?

CCR users are potentially vulnerable to a CO2 hit but if we pack our scrubbers properly (not a difficult task), keep our underwater exertion under control and most importantly change our sofnolime on a conservative basis, we should be ok.

You only have to look at the earliest mobile phones compared to today's wafer thin Sony Ericcson 880 to know that CCR technology will develop to include a credible CO2 monitor.

Some might agree that a BOV is the best alternative to a CO2 monitor until one is available?

Charlie

nigelh

A BOV solves other problems while a CO2 sensor just tells you to 'get off the loop'. They will need to be good as multiple false alarms at depth could be add up as dangerous as the fault it detects.

I'm a bad gadget freak but even I fail to muster much excitement for a CO2 sensor. I've had one real run in with CO2 and one scare but the first caused me to buy a BOV and the second to switch to it. I'm not convinced that it would actually do much for my life expectancy unless I made a habit of pushing the scrubber way over it's time but the projected price of current sensors would buy an awful lot of Sofnolime.

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nigelh

Ben Field

Sorry DSOTM but this makes for troll reading IMO....

I'm afraid I have to dissagree, price, training requirements and further developement of OC gear mean CC will always cost more to run, service and dive. No Red Sea rental cowboys could be trusted to prep even the simplist rebreather, let alone one with complex multiple sensors.

The % diving rebreathers will grow, no doubt, but it will remain a minimal % IMVHO.

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