Is there a simple solution to CO2 break through?

onetime

Yeah, I understood that but also threw out the possibility of sorb in the hose on the initial post. Just want to keep a bunch of ideas out there for comment to see what comes of it.

--Paul

onetime

I've seen them in an earlier thread. Interesting but it's not really addressing the break through possibility on existing units.

caveseeker7

Just going by the title question, I'd say be diligent with your preparation, pre-dive and stay within manufacturers ratings is a good start.

If you're choosing a rebreather (rather than having one already) pick one with a good scrubber design that's well tested. OMG, SMI and the various MK16 iterations. Such designed units should reduce the chance of having breakthrough in the first place, which I consider the ultimate goal.

The Micropore seems like a contender, too. I hope more data and experiences will be available soon, as that design should almost eliminate channeling and very much caustic cocktails.

The rEvo also looks good, I wish there was formal testing data available.

CO2 sensing technology will eventually come, and I hope it will be in the form of (a) system(s) that can be added to existing units, and hopefully at a reasonable cost rather than $$$ replacement electronics including new controllers with deco cpapbilites etc, etc.

For axial scrubbers the temp sensor idea is a step in the right direction. CO2 detection will work either with or without it. I truly hope Tom Rose is successful with his design as it should be able to be implemented on most scrubber designs and pave the way for CO2 detection.

__________________
Cheers
Stefan



"Political Correctness is a doctrine, fostered by a delusional, illogical minority,
and rabidly promoted by an unscrupulous mainstream media,
which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.!"

Mdemon

Please forgive me Paul!

All well and good, but the matter being addressed is how to design out potential problems. The Inspo rocks and has been tested to the nth degree. However, if you screw up, you can still take a hit. Mk15s are also not immune to overbreathing, regretably.

So, why not address the matter head on? What's the downside? In my plans, one extra piece and one modification. The payback? CO2 breakthrough immunity(-ish), reduced running costs and potentially extended duration.

If it works...

I think if you're going to test for breakthrough, you might as well have something which will deal with it at the same time...

__________________
www.southwestmafia.com

"small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!"

The WRONG Attitude will get you killed.

"Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"

UWSojourner

My understanding is that CO2 causes the blood pH to drop below what is normal. Until someone comes up with a great way to detect CO2 in a Rebreather environment, might there be a way to directly test what is occuring in our blood? I'm thinking of those nifty small units you put on your finger that tells you your oxygen levels.

silent running

Hello all, I agree with Stefan. Choose an Rebreather with a properly designed scrubber in the first place, pack it well, pay attention to the rated time and you should be fine. If a particular scrubber design is prone to quick breakthroughs or can be over-breathed easily, choose another RB.
IMHO, anything which increases the WOB should be avoided. Higher WOB will only increase the likelyhood of CO2 production, especially on deep dives. Which is when you would presumably be most worried about scrubber breakthrough. So would it really be worth it? Also, I think most divers would think of the 2 small scrubber design the same as if it had 1 big scrubber and dive it that way. I find that filling 1 scrubber on the deck of a pitching boat is enough work for me, 2 would be twice as unfun.-Andy

Mdemon

There's that word again!

I've enjoyed diving my Inspo under exactly the conditions you describe. I have no problem though with trying to insure against the time things don't go according to plan.

Good point about WOB though. This needs some very careful handling.

__________________
www.southwestmafia.com

"small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!"

The WRONG Attitude will get you killed.

"Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"

silent running

Hi Mdemon, not trying to slag off the whole idea or anything, I just think it's problematic. My understanding is that Axial scrubbers in particular breakthrough faster than radial ones. I think this might be why Alex has done his Rebreather design with 2 micropore scrubbers. So in some respects, this idea is already being implemented in other designs, like the rEvo. If there was a way to keep the emergency scrubber out of the loop(which seems difficult as it would then be at a different ambient pressure)and then actuated with a manually operated valve of some kind, and wouldn't effect the WOB during a normal dive, then OK. But I can't imagine any easy way to do it. Also, if there's any effort involved with the engaging of an emergency scrubber(like reaching for and turning valves)or any delay in having it kick in, your still going to have to bailout to OC and this may not be so easy to do, as suggested by a number of people who had CO2 hits-they were almost incapacitated at the onset. So aren't we just talking about a making a bigger scrubber then?-Andy

onetime

No, it's not just about a bigger scrubber. If anything it's more about two different kinds of scrubbers to overcome the potential flaw in the main scrubber. If the main scrubber can be overloaded with exertion, what's to say simply doubling the same design won't be?

Manually operated doesn't work, as you outlined, because it will likely be too late (and isn't that what bailout is for anyway?) by the time you feel the effects and you may not be able to make the switch.

The discussion here isn't about "following guidelines" of the manufacturer as stefan talked of but of compensating for a flaw or flaws that appear to be resident in a number of designs. Flaws which we don't currently have a clear picture of.

What we know:

CO2 is getting through some existing scrubbers despite following guidelines for sorb packing, pre-dive tests, and sorb time limits.

Evidence:

Many stories of suspected CO2 hits despite following protocols.

What this thread is about:

Finding a safer way of doing things by generating discussion and examining the subject.

A bigger scrubber fits if the topic is extending duration of a unit, it doesn't fit this topic, IMO.

--Paul

silent running

Hello Paul, I was trying to narrow it down and figure out exactly what direction you all were going in. Thanks for summing it up. Now, if you add a second scrubber, how do you keep from raising the WOB?