co2 hits? bov or not

[uwxplorer]

Like Mark, he is saying that if you ever encounter a hungry shark, the only thing that may save you is a mail coat.
Since you can't be sure you will never meet a hungry shark, you should always wear a mail coat.
This is called "plain thinking" down under.
Where they definitely do have hungry sharks.
I am personally still looking for a mail coat that won't make me sink to the bottom (and raise my CO2 due to over-exertion).
And I am trying my best to avoid shark infested waters...

 

[scubainchicago]

After being brainwashed during my Fundies class about CO2 narcosis based on the flimsiest shred of evidence (to the eye of a skeptical scientist), I have developed a serious case of allergy to the term "CO2 narcosis".
Would someone mind providing first hand description of CO2 narcosis versus incapacitation due to CO2 buildup in the bloodstream, which to me is physiologically different: there are a lot of ways CO2 can apparently affect our normal state, with some capable apparently to result in panic (which can hardly be assimilated to "narcosis").
But my point is not so much to argue about semantic, than to figure out whether or not ways of detecting CO2 build up can be learned (and therefore taught).
The recent study let by Simon Mitchell about prebreath stopped short of addressing this issue at the surface, by not testing subjects who had failed to detect a missing scrubber (or a missing O-ring) several times after their initial failure, to check whether subtle symptoms could be learned. Maybe after all, besides detection by fancy medical gizmos, it is possible to become aware of something abnormal going on in our physiology, thought process or bladder function, which we could use to anticipate those cases of high internal CO2.
To me the arguments of the kind "I got a CO2 hit and I survived because I had a BOV, therefore anyone without a BOV, however good their reasons are, will die when they suffer a CO2 hit [implicitly suggesting that everyone doing challenging enough dives will experience one]" are getting tiresome and are not fundamentally helpful without a thorough introspective analysis of what led to the event. If what led to the event was a series of bad decisions, but the ego of the person prevents him or her to clearly state that, then I am not learning anything.
Surely driving without a seatbelt, above speed limit and passing cars in curves with no visibility raises you chances to die in a car accident?

Our bodies subconscious drive to breath is driven on expelling CO2. David Shaw would be a good example of a CO2 hit/ hypercapnia. He packed his scrubber with a finer scrubber material increasing his WOB. His choice of bottom gas without a high helium content also contributed to a high WOB at depth. Adding all that together with his working hard at depth was too much for him to overcome. I don't know what his bailout plan was, but he never left the loop and ultimately died because of it.

 

[Randy Thornton]

I know there are several different thoughts and philosophies on BOV use. My take on it is that the BOV is a transitional device while I ultimately move to my off board bailout 2nd stage.

 

[Brad_Horn]

(Facepalm) OK, I'll take your word for it that the majority of the worlds rebreathers aren't interested in a BOV, Shrimp sales suggest otherwise...

Ben, I fully agree there is a very good market for L-R BOVs; however, at this time there appears to be an insufficient one, for BOVs of "known" performance.

Why is yours R-L when "everyone" else's is L-R?

There is quite a spiel in the documentation about it, but it boils down to that is what clients expect as the available professional CCRs are all R-L flow, be it for commie, military etc. See Divex, Drager, Carleton, Cobham, SIVA, Aqua-Lung rebreathers.

It wouldn't surprise me to learn that the only reason that the rEvo also matches this, is that Paul did it so the flow arrow molded in the top, of the off the shelf and therefor cheap to source Drager DSV was pointing in the right direction.

Or are you suggesting I reverse the flow just to make buying a different BOV an option!?

My question, actually was. Why have you made your flow on your homebuild the way you have?

In answer to your question. If the flow is untested in the first place, what does changing the direction do if all other factors remain unchanged?

I know on one unit if you did a rapid buoyant ascent, and injected O2, the diver didn't get that O2, it got sucked out the OPV, due to the expanding gas and they went hypoxic. It is irrelevant to me if this issue has been fixed, but it is one of the hazards in having the wrong gas flow. Taking that as an example, it might actually be safety to either change the direction of the flapper valves, or fit the OPV on the other CL. But you have to test the unit to know this. The recorded PPO2 for deco is really irrelevant if it is not close to what the diver is breathing on ascent.

If you start to sell an MCCR with sensors inside the case (no pods) with a wrist monitor and an adjustable flow orifice drop me a line ;-)
FWIW- The unit Mark is diving looks modified to me- 3rd Party pod, 3rd party Computer/Monitor and 3rd party Harness

Ben, maybe! There is a lot more flexibility in getting mCCRs and eCCRs CEd now with the 2013 version. Still can't see any means to get a user adjustable flow orifice through but that is what engineers are for if there is sufficient justification.
as to your saying modifications. What is modified? Purpose designed POD, suitable PPO2 monitor for mCCR use and a one for one harness to better suit the user. The Rb appears completely unmodified (though probably has a drop-in kitty litter scrubber).

this thread is BOV focused and I really don't understand your argument that their is no market for a ALBOV plumbed the right way around,

Ben, Lets try and crack this nut another way about having the ALVBOVs performance on a rig plumbed the wrong way around.

Do the folk who are buying L-R BOVs not have a clue what their performance is? Answer has to be yes. Okay, so Joe Bloggs has spent $1k on a BOV already or his unit came with one. Joe Bloggs has done his research and read everything that the likes of Simon Mitchell have published and can see that no one knows if having an honest low WOB BOV is critical or not, so assumes it is only a nice to have. In any regard he probably has no clue what the WOB of his unit is anyway.

Why would he spend another $1k+ on a better BOV, with the lowest WOB in both OC and CC modes, if what he has appears to be sufficient already? Especially if his BOV is indeed already sold as having low WOB even if in reality it is 2+ times higher!

I am plucking the figure, but the MOQ to make it worthwhile OSEL tooling up to supply a CE certified to EN250 and EN14143 L-R flow BOV with the same best in class performance of the ALVBOV is probably in the order of 1000 units per batch. It may even need to be 2 or 3k to justify the upfront costs! You starting to see where I am going with there not being a viable market for OSEL to supply non-core kit to fix other manufacturers problems?
I know that some folk want better kit than they are currently being flogged and would jump at being able to actually buy best in class stuff with "known" highest performance as there is certainly currently an unfilled niche, but OSEL is not a charity. The ALVBOV is available to anyone that wants to buy one R-L, if needed.

My take on it is that the BOV is a transitional device while I ultimately move to my off board bailout 2nd stage.

Randy, why only transitional? What does your off board bailout 2nd stage offer, that your BOV does not? I am assuming here that the source gas is the same as the 2/3L diluent argument v AL80 stage is pretty obvious.

As per Paul Haynes talk that you also? attended at OZTEK, with regards CO2 would there not be quite some benefit to you staying on the BOV on OC and making use of the retaining strap benefits, if that is the reason you have bailed out?

 

[Mark Chase]

So I don't get your reasoning here. I assume you retained CO2 on a perfectly good high flowing OC reg, but on CCR you think a reg built into a BOV that most likely flows less gas is the answer to your CO2 problems?

Sent from my HTC Desire using Tapatalk 2

The logic is two fold

1: if the CCR is the cause of the C02 you need to get off closed loop and for this you need a BOV

2: If the C02 is retained C02 as was obviously the case when getting a C02 hit on OC, you need to get on to a known safe gas as a confidance boost. No mater if you have C02 alarms or not if your breathing like a train youwont beleive its not a CCr related hit till your on a safe gas.


Thers a third issue as well

My old Golum Mk1 BOV was not noticably worse to breath OC than my Apex ATX40s on DS1s.

I have in the past dived ATX40s tuned so light they would free flow at the slightest provacation if not in the mouth and thats lovley for OC diveing but no good as a bailout reg. So my off boards are detuned a bit.

My Shrimp BOV on OC is not bad but not as good

Then thers the forth issue

Having a BOV enables you to go OC without removeing the loop which could be impossable if your breathing hard and also could result in the incident pit if you flood the unit during the panic of doing the swap.

If you BOV is not as good as your OC reg and it IS possable to swap to an OC reg then do so after the initial bailout.

Best of both worlds.


Another issue we have not discussed is long hose buddy diveing.

In cave diveing the bailout scinario would be to use half your own gas than use half your buddies gas so as to maintain a reserve. So if your donating the long hose on your bailout tin to your buddy and you have a BOV you still have a personal bailout option via the BOV


ATB

Mark

 

[Ben Field]

My question, actually was. Why have you made your flow on your homebuild the way you have?

Because I used parts that where already that way around as the majority of available parts are... but its irrelevant.

I know that some folk want better kit than they are currently being flogged and would jump at being able to actually buy best in class stuff with "known" highest performance as there is certainly currently an unfilled niche, but OSEL is not a charity. The ALVBOV is available to anyone that wants to buy one R-L, if needed.

Obviously I understand that, I said it in my first post- my point remains, the majority can't use your BOV but you push it anyway, why bother? Its like taunting a child with ice cream then giving them lemons.

Its simply not an option. The next time someone asks what RB? Perhaps I should suggest an Vanguard Nuclear Submarine instead- it'll work but its not "off the shelf"

 

[Captain Starfish]

Ignoring the pox and trying to get back to topic briefly...

One thing I've not seen mentioned is the ease of "sanity breaths" with a BOV.

You're swimming along, things get weird. If it's all too hard to switch you can very easily convince yourself that she'll be right mate. Flick a switch, take a couple clean breaths off OC. No different? Back on the loop, it really was nothing. Otherwise you have some proper bailing out or at least problem solving to do.

This is the big difference the BOV has made for me. When I doubt - any doubt - flick the switch, take a couple sanity breaths then decide what to do. Easy.

 

[DeepUnderground]

I was in a bar in Malta with two estimed rebreather divers a few years ago, apparently when tested by vr the inspiration scrubber works better with the flow reversed

 

[Ben Field]

I was in a bar in Malta with two estimed rebreather divers a few years ago, apparently when tested by vr the inspiration scrubber works better with the flow reversed

Would you trust anything tested by VR since they make the most complex and unreliable rebreathers in the world?

You can reverse the Inspiration loop at the front without impacting the flow direction in the scrubber and why would you unless you also relocate the sensors!!!

 

[rjack]

Randy, why only transitional? What does your off board bailout 2nd stage offer, that your BOV does not? I am assuming here that the source gas is the same as the 2/3L diluent argument v AL80 stage is pretty obvious.

Your magical BOV prevents caustic too?

 

[Randy Thornton]

Randy, why only transitional? What does your off board bailout 2nd stage offer, that your BOV does not? I am assuming here that the source gas is the same as the 2/3L diluent argument v AL80 stage is pretty obvious.

As per Paul Haynes talk that you also? attended at OZTEK, with regards CO2 would there not be quite some benefit to you staying on the BOV on OC and making use of the retaining strap benefits, if that is the reason you have bailed out?

Brad, probably the most obvious reason would be so that I can easily switch between bailout bottles at gas changes, share bailout bottles with team members, and rotate bailout bottles depending on the circumstance. Much more flexibility without being tied into complicated manifolds, potentially incompatible whips, etc. Going to a BOV at bailout gives me immediate access to OC gas while I am fumbling around to locate and deploy my off-board bailout reg.

 

[Mark Chase]

Your magical BOV prevents caustic too?

You cant get caustic coctail on a Apoc

or any other unit that uses toilet role scrubbers

ATB

Mark

 

[rjack]

You cant get caustic coctail on a Apoc

or any other unit that uses toilet role scrubbers

ATB

Mark

I have heard this but also heard the opposite as well. But this assumes you switch units not just use Brad's BOV.

While it does flow the "correct" direction for me (R-L), its not available here so I couldn't use one even if I wanted to splurge for it sight unseen.

 

[PeterN]

While it does flow the "correct" direction for me (R-L), its not available here so I couldn't use one even if I wanted to splurge for it sight unseen.

Sure it is available to you. Just send off your money and wait, and wait, and wait...

 

[Simon Mitchell]

Joe Bloggs has done his research and read everything that the likes of Simon Mitchell have published and can see that no one knows if having an honest low WOB BOV is critical or not, so assumes it is only a nice to have.

Brad,

Can you please explain what you mean by this? I don't understand it.

Simon M

 

[Mark Chase]

Brad

As you know I came close to buying a APOC BOV because it had a v low WOB, but because the direction of flow was wrong for my unit, I didnt buy one.

I think we all want a combination of compact efficient design and low WOB but we are not going to compromise on loop flow direction in order to get something that's not noticeably better than a unit like the Shrimp


Sadly for you we can't comprehend the difference in WOB figures you offer out. If you say one car does 30mpg and another does 35 we understand it immediately but the numbers you offer are meaningless to us. We just breathe it and say its OK or not OK

I am sure many will put up with a worse (but tolerable) WOB if the unit is well designed and compact.

I can also say without hesitation that I dont even notice the WOB until I am doing a long dive. Best test for WOB for me is cave diving. Constant work phase with higher SACs and the WOB soon begins to take its toll.

On a "normal" 120min dive I hardly notice.

In emergencies its the WOB of the OC reg that counts.

The Apoc unit is very good but they need to bite the bullet and get a reverse flow option or they will have an extremely limited market place. Even rEvo divers will avoid them because with any other BOV they can reverse the flow and sell on if they want too.

Apoc BOV

ATB

Mark

 

[MeRodent]

There's also the issue of servicing the BOV.
From my understanding the apoc BOV needs to be factory serviced. Whereas I can pull the SHRIMP apart and service it myself.

 

[Mark Chase]

There's also the issue of servicing the BOV.
From my understanding the apoc BOV needs to be factory serviced. Whereas I can pull the SHRIMP apart and service it myself.

I am sure they would prefer factory service but I am equaly sure you can do it your self

Remeber when you couldn't get service kits for Apex regs

If its humanly possable to service and doesent have some secret lock out code then I can service it

ATB

Mark

 

[lof]

You cant get caustic coctail on a Apoc

or any other unit that uses toilet role scrubbers

ATB

Mark

I can assure you that you can get a caustic cocktail on toilet roll scrubber. I did.

 

[Brad_Horn]

Your magical BOV prevents caustic too?

When fitted to the right rebreather system yes. If you get water in the loop you just purge it out. No water sitting in the scrubber = minimal caustic risk. There are certain advantages to diving a fully flood recoverable rebreather fitted with an EAC.

Unlike when kitty litter gets wet there is a latency with EACs that mitigates the caustic cocktail risk. https://www.facebook.com/151298954899613/videos/vb.151298954899613/986242151405285/?type=2&theater

Brad, probably the most obvious reason would be so that I can easily switch between bailout bottles at gas changes, share bailout bottles with team members, and rotate bailout bottles depending on the circumstance.

No worries Randy, but none of these reasons appears to have anything to do with the immediate period of any bailout scenario?

Much more flexibility without being tied into complicated manifolds, potentially incompatible whips, etc. Going to a BOV at bailout gives me immediate access to OC gas while I am fumbling around to locate and deploy my off-board bailout reg.

How do you handle bailout when running a hypoxic diluent?

Agree that availability and standardisation of simple off board QC bailout setups with sufficient flow to pass EN250 for a BOV would be nice to see someday.

You cant get caustic coctail on a Apoc

Mark, you can, you just must have flooded the unit for >10min (closer to 45min) and not bothered to purge the water out of the scrubber and then do a few tumble turns wearing it. Easy to see how much water is in your buddies can when your doing flood recovery training, as with the lid off, the scrubber window acts as a tide gauge!

or any other unit that uses toilet role scrubbers

Depends on their design. Some are designed such that the EAC is sitting in a pool of water when flooded with no means to recover from the flood. This eventually leads to a caustic issue but still not the immediate issue you have with kitty litter.

While it does flow the "correct" direction for me (R-L), its not available here so I couldn't use one even if I wanted to splurge for it sight unseen.

You have lost me. Why is it not available to you there?
No reason that I can think of that OSEL cannot have one drop shipped this week to Wakulla Diving in Florida if you do not want to order direct.

Plenty of Apocs in the US. and there is at least one Boris kicking around there with an ALVBOV on it. https://www.facebook.com/1512989548...1298954899613/151310698231772/?type=3&theater

"Joe Bloggs has done his research and read everything that the likes of Simon Mitchell have published and can see that no one knows if having an honest low WOB BOV is critical or not, so assumes it is only a nice to have.***8220;

Brad,
Can you please explain what you mean by this? I don't understand it.
Simon M

Simon, put simply. At what specific point (line in the sand) does the WOB of a BOV/OC reg become unsafe to bailout from a rebreather, be it a CCR with a WOB of 1.44J/L, your Mk15.5s 2.1J/L or your current units ~2.99J/L?

At the moment we know a BOV is good to have but as above Joe Bloggs doing his pre-BOV purchase research does not know how critical (or not) it is to have a good, mediocre or poorly performing BOV. What we as a diving community do NOT know (other than what is in the EN250 requirements) is how ***8220;low" do we need to have the WOB on the OC side, as a maximum, in order to be safe when bailing out off a rebreather? ie. Can the BOV OC mode be as high at 2.5J/L at 50m on Air at 62.5lpm (which is the worst case example of a CE marked OC reg) or must it be closer to a good OC reg at around 1J/L like an Apeks or Poseidon one?

As an example:
Your current CCR has a WOB somewhere between 2.75 and 2.99J/L depending on if it is APD or NEDU doing the testing.
Your OCB has a CC mode WOB of approximately 2.13J/L (based on my guessing from APD saying this is comparable to their DSV) and an unknown to you OC WOB, correct?
As your OCB has unknown WOB that is probably 2.5times that of a good OC reg (you know it at least passes EN250 so that is something), can you categorically say that is safe to bailout to?
If the answer is ***8220;yes***8221;, is it purely because it is lower than your current CCRs entire loop WOB?
If the answer is ***8220;yes***8221;, does this mean that BOV users need to know their OC BOV WOB is less than their units CC mode WOB?
at what point is your OCB unsafe to bailout to based on gas choice and depth? Why?

or would it be simpler and more logical to just say it is safer bailing out to a BOV that has an OC WOB comparable to that of an OC reg?

As you know I came close to buying a APOC BOV because it had a v low WOB, but because the direction of flow was wrong for my unit, I didnt buy one.

No worries.

I think we all want a combination of compact efficient design and low WOB but we are not going to compromise on loop flow direction in order to get something that's not noticeably better than a unit like the Shrimp

1. What are you compromising with a R-L loop flow?
2. Your saying that a 2.5x difference in WOB for the CC mode is not noticeably better?
3. AFAIK there are no L-R BOV options that offer a compact efficient design and low WOB, except possibly the Poseidon BOV, if they ever test it.

Sadly for you we can't comprehend the difference in WOB figures you offer out. If you say one car does 30mpg and another does 35 we understand it immediately but the numbers you offer are meaningless to us. We just breathe it and say its OK or not OK

I am sure many will put up with a worse (but tolerable) WOB if the unit is well designed and compact.

I can also say without hesitation that I dont even notice the WOB until I am doing a long dive. Best test for WOB for me is cave diving. Constant work phase with higher SACs and the WOB soon begins to take its toll.

On a "normal" 120min dive I hardly notice.

In emergencies its the WOB of the OC reg that counts.

Mark, and I completely agree with you, hence my question/point to Simon above.

at the moment when purchasing a BOV buyers are where divers were with OC regs 20 years ago. At which point in 1996 folk like John Bantin identified that you needed to compare more than just subjective things like colour and size.
and they realised that in emergencies it is actually important to be diving an OC reg that has an actual provable low WOB and therefore verifiable performance under high workloads.

If you dive a lower WOB unit, then when cave diving you will not need to work as hard in the first place. This seems a simple concept unless I am missing something obvious.

The Apoc unit is very good but they need to bite the bullet and get a reverse flow option or they will have an extremely limited market place. Even rEvo divers will avoid them because with any other BOV they can reverse the flow and sell on if they want too.

Mark, What is in it for OSEL selling to the L-R crowd? All OSEL rebreather are and will be R-L.

With regards rEvo users. The ALVBOV is there to buy if they want to lower their CCRs WOB and have the lowest OC bailout WOB option and fit a CE certified to EN14143 and EN250 BOV.
If they are happy diving a higher WOB CCR then fitting the Shrimp to their rEvo will not bother them. Nor will the fact they do not know the OC WOB of the Shrimp for bailout. But in this case, they almost certainly wouldn***8217;t buy an ALVBOV anyway!

OSEL is only selling the ALVBOV as a standalone component because it is a spare part for their rebreathers and there is a reasonable demand for them.

There's also the issue of servicing the BOV.
From my understanding the apoc BOV needs to be factory serviced. Whereas I can pull the SHRIMP apart and service it myself.

You can pull an ALVBOV apart and replace everything yourself as well and OSEL will sell any parts/seals as spares. BUT the reason it is specified for factory service is the factory has the test equipment to fully leak check the ALVBOV and trained technicians to do the work.

The ALVBOV has tight tolerances on most parts because it is injection molded and to get the desirable high performance.
It also has things like a 3D lip seal separating the OC and CC sides, such that if you descend with the diluent gas off, you do not wreck your regs diaphragm or exhaust flapper valve. The pressure is equalised on descent. No other BOV offers this.

Remeber when you couldn't get service kits for Apex regs

If you cannot find a spare part for anything OSEL sell, you can either order it as a one off special spare from them, they will sell you the complete sub-assembly if that is not a user serviceable item (oxygen injector as an example) or they will add it to the webshop as an individual spare part.

I can assure you that you can get a caustic cocktail on toilet roll scrubber. I did.

Jakub, I presume you did this deliberately and knowingly had the scrubber flooded for a significant point in time? See above video