BOV, yes or no ??

Flup

Hi All,

I'm quite new to this list and got certified just 2 weeks ago on my MEG. So now i realy want to learn to dive this masterpiece of diving art. I've been sniffing around here now for a few weeks and stumbled upon the BOV, so what the hell is that i wondered. A completly new subject to me.

For what i can make of it it's a switchblock to go from cc to oc (maybe i'm wrong here ??). Now my qeustion to you all is: What exacly is a BOV, should i get starting using one and what are the benefits or disadvantages from (using) a BOV.

Please give me some answers, still trying to learn.

Kind regards

Flup

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JonnyB

A BOV or OC/CC DSV is a DSV which has a regulator attached to it and by the switched of the knob you get fresh gas.
It can be a lifesafer cause you have access to good gas in the matter os a split second but also it means much more complication and more failure points. You would have to weight the good and the bad against each other and decide for yourself.

I can tell you how i reasoned on my KISS that i had.
1. Connect the BOV to offboard gas to switchblock and quick disconnects. Cause you can drain a 3L diluent in matter of seconds at depth and you might not always have breathable gas in diluent bottle at all depths.
2. My BOV on my KISS did not perform very well below 65m, it started to freeflow and was heavy to breath from at other times.

just my 2cents

/Jonny

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Gibbon

BOV = Bail Out Valve.

One advantage is that you dont have to take the loop out of your mouth to go OC should you need to.

Flup

Hi JT,

U've got a strong point there, and i'm not into rushing into any changes tommorow, just want to learn and get some feed back, so may the time come i do consider any changes i can make a good choice.

You're never to old to learn some one told me once, that's why i asked the qeustion.

Thanks for your reply

Silent greetings

Flup

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Mdemon

Not rushing into adding a safety feature? Hmmm... I'm a big advocate of BOV's and I'd suggest they're even more useful to a new Rebreather diver than an experienced one. My 2p, as a fairly new RB diver (and BOV-user).

The difficulty you will have is choosing and sourcing one. They are also not cheap... Do a search here on Rebreather World and you will quickly find threads showing your options.

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

Mark Chase

I agree with John on this.

BOV seems an obvious enhancement in safety on any CCR. Unfortunately the existing choice is not straight forward and they do have issues so its not an easy step to take.

The whole act of getting hold of a back up reg, closing the loop and bailing to OC is a lot to ask of a diver having a serious issue on a unit.

(well i found it a struggle anyway )

A bov is so simple to use.

CO2 hits should never happen but they do and all the divers I know who have suffered it had a massively hard job bailing to OC. A BOV is just a simple twist of a lever and its Job done.

Experimenting with a KISS bov at the moment. Ill probably run it off board direct to a large bailout cylinder and gag it to my head.

ATB

Mark Chase

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Deepwreck

Having dove the KISS, and now moved to the MEG, I can add some light on this issue. I liked the DSV on the KISS, as an easy to use and fast way of bailing out on the unit. I still found that I had to take the DSV out of my mouth and switch to OC bailout within a few breaths anyway. So the real advantage to diving with one is the second where you become aware a problem exists, and before you get off the loop entirely. This moment is where you can flush your lungs with, depending on depth and dil gas, hopefully breathable gas to wake you up and turn your brain back on.

However your back gas just isn't enough to bailout on, and for deeper dives you may only get one or two breaths before your cilinder is empty. Machanicly the act of turning a nob, or pushing the ADV are similar, and I would argue that the value of the gas being breathed in such an emergency is more important that bailing out, in those first few seconds.

Doing a Dil flush on the MEG Should give you breathable gas, and either way would give you the same gas supply as a BOV would given that they are both linked to the Dil tank. So in my mind, the question comes down to Turn a nob, or push the ADV. Either way you may still have to go to OC if the problem can't be fixed, but in the case of a Dil flush you know you have breathable gas in the loop. In the BOV option you would have to go back on the loop and flush to recover from a problem or stay off the loop and Bail to off board OC gas.

On my KISS I added an Off Board gas addition port so I could plug in my OC bailout gas to the unit or pure 02 without taking the loop/DSV out of my mouth. I found that if I was going to fully bailout from CCR I didn't want to be on the DSV I wanted to go to my OC Regulators, and have the option of handing off my half empty tank to my buddy for another full OC tank. Giving him/her the option of bailing out themselves.

On other words I have no plans to add a BOV to my unit, I choise to use the dil flush, SCR, on loop OC, and then OC bailout, depending on the nature of the problem. I will stay on the loop for as long as possible without endangering my life, and I carry enough gas to bailout from my deepest, longest point. As leon teaches once you leave the loop you shouldn't go back on it.

Personaly I will do anything to survive, and I know that using the supply of gas to my advantage is crusial to that survival.

Everyone has the right to chose the best option for them, and I don't want to say anyone is wrong by choising another way. So with the gear you have practice your bailout drills, and become comforitable in the water with your style, and gear configuration. It wont matter what you have with you if you cant use it smart.

divetheworld

100% agree, cant add anything more to this argument. If you can afford one, get one. If you cant, save up.

Brent.

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Mdemon

For deep stuff, most people I know plumb the ADV inboard but the BOV offboard. The ADV regs are usually detuned in my experience and hard WOB, but as you point out, will give a few sanity breaths "open loop". My drill is Open Loop then BOV asap, but Open Loop is really hard work on my unit, I'd find it very difficult if my breathing rate went through the roof.

I looked into using the dil inflators like this for bailout in just the way you describe. My unit is different so I can't comment on your inflators; what I can tell you is that mine simply do not deliver enough gas to bail from at depth and at a high RMV.

True, and even with a BOV you will have to reg switch on ascent (unless using GCS fittings). However, the strength of the BOV is during those first moments of bailing and until you have got yourself together. With the dil flush, you still haven't fixed a CO2 problem - just got yourself in a position where there's temporarily less CO2 in your loop. You'd still have to bail, and quickly. With the BOV, you give yourself more time to think and get off a problem loop quicker.

I'd rather get off it quick, sort the problem and get back on. Just a difference in training I guess.

Fair enough.

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

Doorduijn, Niels

Hi Flup,

I have been looking into the question of using a BOV for some time now and I decided sometime ago that I will get one on my new unit. My reasoning is as follows.

I believe that there is only one real reason why you would want an BOV: a CO2 hit. There is ample anecdotical evidence that people who suffer a CO2 hit are often physically unable to make the switch from CC to OC. So, if you have a CO2 hit, then being able to switch without taking the regulator from you mouth seems like a possible live saver. As others have mentioned in their postings, the BOV needs to be attached to an outboard gas source to be usefull, not only because you will empty a 3l inboard at depth pretty quickly, but also because if you are suffering from a CO2 hit, you will be breathing like there is no tomorrow.

Obviously, there are other situations in which you may have to bail out (high PpO2, low PpO2, flooded loop), but in those situations the difference between a BOV and switching to a bailout regulator (bungied around the neck) to me seems less of a difference.

To this you have to balance the disadvantages. There are not many BOVs on the market and I have heard complaints about most of them. A common problem seems to be that the negative pressure test becomes impossible or very hard to do. I would argue that for a beginning rebreather diver, the need to do a proper negative test is more important that the benefits of the BOV (you will not be making 100 meter cave dives with the unit this month, right?). Moreover, I have heard that many BOV have a pretty high WOB. In addition, a BOV will increase the drag of the hose, but I do not know whether that is really significant.

For me, the CO2 argument has, at the end, won the argument. I am now waiting for APD to bring their BOV on the market. It is supposed to become available sometime this year. APD tends not to rush products into the markets so it may take more time but most of their products are in my view very nice. I forgot the technical term, but APD can mold plastic into shape, which means that their BOV is likely to be much smaller than anything presently in the market. (If you look at some pictures on the internet, you will see that most BOVs are cut from a piece of delrin, hence they tend to be big). A smaller unit also means that the distance between the mouth and the membram (?) of the BOV will be less, hence a better WOB.(at least that is my understanding).

Rgs,
Niels Doorduijn
Holland