Off with the BOV

[Lancer4545]

Hi Lance. Can you state what you base this assertion on?

Hi silentbob, Anyone who has experienced a severe CO2 hit will tell you they couldn't hold their breath long enough to remove the DSV and go to an OC second stage. I have experienced this first hand and I can confirm it. You might be able to swap over with a mild CO2 hit but go deeper and things only gets worse much quickly.

The only real answer is a BOV as you now only have to flip a switch to bail out. There are many different BOVs and sometimes even a quality BOV will not provide optimum performance and that's where regular servicing and proper set up makes all the difference.

 

[Lancer4545]

Gee Lance, could you possibly be more patronizing ?

Peter

Hi Peter, I'm sorry if I offended you but what part of my post do you not agree with??

 

[cardysnr]

I have experienced this first hand and I can confirm it. You might be able to swap over with a mild CO2 hit but go deeper and things only gets worse much quickly.

Hi Lance,

Can you share more detail on the severe CO2 hit, depth hit occurred, speed of hit from noticing 1st symptoms etc.,

David

 

[Paul Haynes]

I've flooded the Sentinel with a counterlung split at the seam (which passed the negative test), attempted flood recovery through bottom of cannister which was only partially successful (due to user being out of practice on this skill and at the 6m stop so concerns about putting too much buoyancy into the lung), completed 30 mins deco with about 1L water still left in the bottom of the can (I poured it out into a 2l coke bottle and it looked about half full), no CO2 symptoms.

I killed the TPM cable but other than that, a bit of a dry out and fix the counterlung with superglue, and it was good to go again that afternoon.

To the OP's question, I got a JJ with a DSV, after about a year I fitted a Shrimp BOV, and I won't be taking it off again.

Tb.

This raises an important teaching point I emphasis to my students, whilst a negative loop test is generally the more searching of the loop integrity leak tests by identifying the source of most leak paths, due to the typical construction of sonic welded counterlungs, a partially separated seam can seal up under negative pressure (positive external loading), however the same failure point is likely to be opened due to increased internal pressure during the positive check. With myself, on 2 occasions the positive has identified a manufacturing fault / leak in a counter lung seam where the negative did not. For absolute assurance of loop integrity it is therefore equally important to do both negative and positive tests and not just the one.

Rgds

Paul

 

[Lancer4545]

Hi Lance,

Can you share more detail on the severe CO2 hit, depth hit occurred, speed of hit from noticing 1st symptoms etc.,

David

Hi David, My experience was in a controlled environment during a course and I now use it as a teaching tool to demonstrate the effects of Hypercapnia to my Mod 2 students. It demonstrates the misconception that a 3 min prebreathe confirms the scrubber is present and it is functioning correctly. It also demonstrates that it's almost impossible to hold your breath long enough to remove the DSV and change to an OC second stage and it gives the student first hand experience with Hypercapnia, the symptoms and effects so they may be able to identify the onset before it's too late to be able to self rescue or do anything to about it yourself.

• With the unit sitting a bench and the scrubber removed go on the loop and change the setpoint to 0.7
• Breathe the unit until the onset of any symptoms. Most students notice no symptoms until around 7 - 7 1/2 mins
• Stay on the loop as long as it is bearable and then hold their breath and swap over to an OC second stage. Most students last between 9 - 9 1/2 mins and most fail to swap to the OC second stage successfully

The interesting thing about this test is that the time it takes to notice any symptoms until it's unbearable is between 1 1/2 to 2 mins and that is at 1 ata At depth the time can be only a matter of seconds from indication of any symptoms until it's almost impossible to do anything about it.

 

[Chris Brown]

After a reasonable time diving my Meg with the Golem Shrimp BOV, I have decided to dive with out it for a while.

I acquired the Shrimp after fumbling while looking to find my bail out reg at depth. I reasoned that I would have been in trouble had I really needed it. Since then I have put about 100 hours on the Shrimp and have few complaints as it is well built and not hard to service. Mind, I have had to service the the oc bit on the side of the road.

But, it is not as comfy as the DSV. When scootering the BOV feels huge. Today's dive with the DSV was a delight and it felt that the breathing was easier. Getting ready to dive and general tank handling was a breeze. The HUD is in a better spot for viewing.

One of my principle reasons for the switch is that it is time for some deeper dives. I am not at all attracted to switch blocks and slider shut offs. I played a bit with them, but prefer a simple and robust system with the fewest moving, or serviceable, parts.

I have also determined that I will not have something in my mouth that I cannot breath. When I have plugged and unplugged the QC6 while diving I have found this to be difficult at best. Yes my rig is run as an O2 breather in the shallows, but what would be the point of having a BOV plugged in to a hypoxic mix at the surface?

Ironically my dive partner was today breaking in a brand new Shrimp on his rEvo.

I was once with someone who had a CO2 hit. However I don't feel that it was undeserved. I feel that there are many things that are more likely to go wrong.

Has anyone else gone this way?

Peter

Yes and Kudos to you for making your mind up and not being persuaded (bullied? ) by the 'BOV or DIE' brigade.

Im actually back on my BOV on my main AP unit at the moment, just to see how it goes really and to make it consistent with all my current training which is mainly BOV supplied units (and in the instance of PADI, agency mandated , ) but I much prefer a simple straight to off board simple approach.

IIRC, you do a lot of hardcore diving, so it may be a more complex process for you compared to say a MOD1 newbie who wants to bail to the BOV because they are unsure if they have a flood / getting co2 etc.

 

[Chris Brown]

Hi David, My experience was in a controlled environment during a course and I now use it as a teaching tool to demonstrate the effects of Hypercapnia to my Mod 2 students. It demonstrates the misconception that a 3 min prebreathe confirms the scrubber is present and it is functioning correctly. It also demonstrates that it's almost impossible to hold your breath long enough to remove the DSV and change to an OC second stage and it gives the student first hand experience with Hypercapnia, the symptoms and effects so they may be able to identify the onset before it's too late to be able to self rescue or do anything to about it yourself.

• With the unit sitting a bench and the scrubber removed go on the loop and change the setpoint to 0.7
• Breathe the unit until the onset of any symptoms. Most students notice no symptoms until around 7 - 7 1/2 mins
• Stay on the loop as long as it is bearable and then hold their breath and swap over to an OC second stage. Most students last between 9 - 9 1/2 mins and most fail to swap to the OC second stage successfully

The interesting thing about this test is that the time it takes to notice any symptoms until it's unbearable is between 1 1/2 to 2 mins and that is at 1 ata At depth the time can be only a matter of seconds from indication of any symptoms until it's almost impossible to do anything about it.

I think this is a great idea, in principle. I would like to know if a) there are any risks to conducting these tests and b) which manufacturers and agencies would be OK with us doing them?

Does anyone else do a practical demo of CO2 in this way? I have heard of it before, but its not something Ive ever been trained to teach or asked to do either.

 

[Paul Haynes]

I think this is a great idea, in principle. I would like to know if a) there are any risks to conducting these tests and b) which manufacturers and agencies would be OK with us doing them?

Does anyone else do a practical demo of CO2 in this way? I have heard of it before, but its not something Ive ever been trained to teach or asked to do either.

Hi Chris

This would not hold up here in the UK should someone from the world of HSE officialdom became aware of it, let alone a lawyer should it result in a stress induced adverse medical event. You can imagine the court scene - "well Mr Brown, let me get this straight for my and the jury's understanding, you deliberately poisoned your student with Carbon Dioxide to demonstrate a lesson in respiratory physiology long since proven by medical experimentation - is that correct"!

There are actually very strict international protocols regarding human experimentation, which is in effect what is going on. However well controlled the situation is and however well intentioned from a training perspective, if it was to result in some form of adverse effect, you would not have a ground to stand on. This is why such things are undertaken under controlled medical conditions with strict parameters and protocols including trial subject medicals by a Doctor.

Rgds

Paul

 

[Chris Brown]

Hi Chris

This would not hold up here in the UK should someone from the world of HSE officialdom became aware of it, let alone a lawyer should it result in a stress induced adverse medical event. You can imagine the court scene - "well Mr Brown, let me get this straight for my and the jury's understanding, you deliberately poisoned your student with Carbon Dioxide to demonstrate a lesson in respiratory physiology long since proven by medical experimentation - is that correct"!

There are actually very strict international protocols regarding human experimentation, which is in effect what is going on. However well controlled the situation is and however well intentioned from a training perspective, if it was to result in some form of adverse effect, you would not have a ground to stand on. This is why such things are undertaken under controlled medical conditions with strict parameters and protocols including trial subject medicals by a Doctor.

Rgds

Paul

Thanks Paul. Thats what I was thinking.

 

[j_b]

I think it sounds like a great idea... I'd rather have my first experience on dry land. The question is, do I warn swmbo what I'm upto before disappearing into the garage for the last time

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[Tim1]

Thanks again

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[apitkin]

This would not hold up here in the UK should someone from the world of HSE officialdom became aware of it, let alone a lawyer should it result in a stress induced adverse medical event. You can imagine the court scene - "well Mr Brown, let me get this straight for my and the jury's understanding, you deliberately poisoned your student with Carbon Dioxide to demonstrate a lesson in respiratory physiology long since proven by medical experimentation - is that correct"!

There are actually very strict international protocols regarding human experimentation, which is in effect what is going on. However well controlled the situation is and however well intentioned from a training perspective, if it was to result in some form of adverse effect, you would not have a ground to stand on. This is why such things are undertaken under controlled medical conditions with strict parameters and protocols including trial subject medicals by a Doctor.

How can it be experimentation when it is demonstration of a known "lesson in respiratory physiology"? If that were the case my medical school has contravened the Declaration of Helsinki on multiple occasions.

In the UK, it is perfectly legal for someone to do this demonstration as long as the 'victim' has the capacity to consent freely and does so.

Of course in the USA anyone can sue anybody for anything, but that hardly proves your point.

 

[Aquanomad]

So Paul is obviously not a huge proponent for a bov. If he were im sure one of the finest available would be coming from him. With that said, and not to derail the fascinating conversation of the legalities behind self induced soft euthanasia, how many co2 related incidents are there on rEvos? I have been a click away from buying a shrimp for years but never have. I pack properly, check my mushies regularly (actually every post dive now), am diligent about optimal loop volume, and dont seem to fall into the co2 retainer category. I necklace my 2nd stage. And practice regularly. For a rEvo specifically where is the smoking gun for a co2 hit?

Bull Shit Filter

 

[FrancoC]

FWIW........ I had to remove my Shrimp, while waiting for o-rings to rebuild it and switched over to the stock Drager DSV on my rEvo. I couldn't believe how light it was! Even with the gag strap, the Shrimp is a heavy piece of gear. Anyways...that switch was over 2 months ago and I'm still debating going back to the Shrimp.
YMMV

Franco

 

[silentbob]

I'm getting one of the Golem DSVs as I think it is important to be able to eyeball the one way valves. I like the drager DSV for its minimalist simplicity and weight but really don't like the inability to see the valves without a screwdriver.

Sure the suck blow test prior to putting the hoses on the unit will let you know about the functioning then and there but tells you nothing about possible debris, perishing etc...

 

[Mattp]

What is really interesting about the journey with CCR is that many users including myself make many changes to our rigs away from manufacturers guidelines down to personal acceptable risk mitigation or at least a perceived risk. I for one have been diving a BOV on my rigs for over 12 years and only recently switched back to the stock DSV as with some changes being implemented instruction must be conducted on stock units, Im not convinced its the way i will deep dive and explore with my kit but then thats a whole different animal. Personally im more concerned about single point failure of a bailout reg supply than a CO2 hit when selecting to use A BOV.

 

[Mark Chase]

If I could convince my self that id never suffer a C02 event id bin the BOV in a second

My concern seems totaly diferent to other peoples? I have very little concern over the scrubber I am 99.99% sure it wont be that but I am acutly aware of by pass issues mushroom valve issues and most importantly retained C02

Which is odd as retained C02 might not necessarily meen you shhould come off loop

BUT I know what wil happen. Ill get a C02 hit, ill be narked out of my brain, Ill desperatly want to get on to a safe known gas and I wont be able too and panic will set in. Then I am screwed

QED I dive a BOV

Its a PITA but I dont like the alternative

ATB

Mark

 

[Chris Brown]

If I could convince my self that id never suffer a C02 event id bin the BOV in a second

My concern seems totaly diferent to other peoples? I have very little concern over the scrubber I am 99.99% sure it wont be that but I am acutly aware of by pass issues mushroom valve issues and most importantly retained C02

Which is odd as retained C02 might not necessarily meen you shhould come off loop

BUT I know what wil happen. Ill get a C02 hit, ill be narked out of my brain, Ill desperatly want to get on to a safe known gas and I wont be able too and panic will set in. Then I am screwed

QED I dive a BOV

Its a PITA but I dont like the alternative

ATB

Mark

I think we all agree with this principle, but there are a couple of concerns.

1 - my ccr guru ninja trainer buddy nearly died from a co2 hit and he ignored his BOV totally.

2 - there are grumblings within the manufacturing arena regarding WOB increases from BOV's to such a degree that some are claiming they could cause a hit in the first place.

3- Many mod 1.5 divers all seem to do what I did. Dive mix ,go deeper than trained and fit an offboard plumbing nightmare that makes it a tad complicated





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[Brad_Horn]

2 - there are grumblings within the manufacturing arena regarding WOB increases from BOV's to such a degree that some are claiming they could cause a hit in the first place.

Chris, That would imply those manufacturers that are grumbling know the WOB of the BOVs in question to enable any truth to what they say!
Surely it wouldn't be a hard thing for them to publish that BOV WOB test data and prove proof to their claims, would it?

That would then give a list of BOVs that might be safer and less safe perhaps to use..... on any particular rb.

Regards
Brad

 

[Chris Brown]

Chris, That would imply those manufacturers that are grumbling know the WOB of the BOVs in question to enable any truth to what they say!
Surely it wouldn't be a hard thing for them to publish that BOV WOB test data and prove proof to their claims, would it?

That would then give a list of BOVs that might be safer and less safe perhaps to use..... on any particular rb.

Regards
Brad

Great idea! Perhaps they could publish some PDF's?


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