Current Views on Hypoxic bailout/BOV Configurations

[Tracy]

My logic for only connecting to the bailout (normoxic and above) is that there cannot be any question of it being a non-breathable gas at any depth (ignore very hypoxic mixes -- out of scope)

I appreciate that you could build in a check to ensure you're breathing from a breathable gas before switching to the BOV. IMHO that adds a step which both complicates the process (flick BOV lever) and delays getting to breathable gas -- the primary reason for using a BOV and not a regulator.

Of course for very deep dives you'd probably be changing the BOV gas as you descend/ascend as the hypoxic mixes would be fatal in the shallows and intermediate/deco mixes are poisonous at depth. (Is this what you mean?)



For now I want a very simple solution: bottom bailout and a quick flick of the BOV lever. Then standard OC protocols for no-tox deco gas switching using their regulators.

My BOV is fed from my offboard tank via qc6 connector, not a switch block. It is plugged into my bottom mix at the start of the dive. The no tox procedure doesn't change, you are plugging in a hose instead of putting a regulator in your mouth. You still verify the bottle you are switching to.
My bailout is also my diluent and I do gas switches as needed. Lots of ways to skin a cat, I find this one to be the safest/easiest. All my tanks still have second stages, I just use the one already in my mouth. It makes venting the loop easier during a BO ascent, it also removes the annoying floating loop in your face.

 

[lermontov]

(ignore very hypoxic mixes -- out of scope)

OP is asking about mod 3 BO

 

[Wibble]

My BOV is fed from my offboard tank via qc6 connector, not a switch block. It is plugged into my bottom mix at the start of the dive.
...
It makes venting the loop easier during a BO ascent, it also removes the annoying floating loop in your face.

That's a benefit of a BOV I'd not considered! Nice one.

 

[KenGordon]

How? I don’t follow this at all? The procedure for a gas switch didn’t change.

Now you have short tails to swap over or some switch block. neither is as obvious as following a hose back from a second stage to a labelled cylinder.

The time I dived with someone doing that I had less understand of his gas routing than I do of the water routing in my central heating boiler.

 

[Tracy]

Now you have short tails to swap over or some switch block. neither is as obvious as following a hose back from a second stage to a labelled cylinder.

The time I dived with someone doing that I had less understand of his gas routing than I do of the water routing in my central heating boiler.

There is a qc6 on a hose that back to the cylinder. The procedure is exactly the same. You verify the cylinder you are holding and then you plug it in. What is the confusion?

 

[KenGordon]

There is a qc6 on a hose that back to the cylinder. The procedure is exactly the same. You verify the cylinder you are holding and then you plug it in. What is the confusion?

I know I am more stupid in the water, and likely even more stupid following a bailout. This scheme adds an extra step and so introduces an extra way to make a mistake. It also adds an extra way to start off in the wrong configuration.

I don’t have quick release hoses on anything other than by bottom bailout as that initial mistake is one I can see myself making.

I also find that the “quick” part of these connectors is not so quick and I can easily imagine being stuck for a bit with no gas actually connected.

On the other hand, without extra QR hoses, I can find and positivity identity the next regular second stage/mix and switch to that with only the usual gas switch risks.

 

[Brad_Horn]

Reassure me that your BOV has a low enough WOB that I can recover from a CO2 hit when I'm hyperventilating more than I ever have before, and with thick gas.

That is a tough ask as it would both require the specific BOV to actually a) be tested and b) the data published.....

AFAIK Open Safety have been the only one to publish their BOVs WOB.... https://www.opensafetyglobal.com/Safety_files/DV_DL_ALVBOV_Breathing_Params_A3_100318.pdf

Once you have that information for each BOV you can then work out which are over and under the line required to recover safely from a CO2 hit. Whatever that WOB line may eventually be determined to be.....