Chris B(Offline)

I have just been reading the old article by GI3 regarding gas switch procedures and was wondering how people switch.

GI3 advocated (maybe past tense as this is an old article)

• ID bottle by depth marking
• deploy reg and put in mouth
• re-confirm bottle by depth marking and turn on.

if you can breath, you are breathing the right gas.

I was taught

• ID bottle by depth marking only and place hand on cylinder knob
• pressurize and deploy hose
• purge (whilst watching the gauge) to ascertain correct bottle
• switch reg.

I like the simplicity of the original although it does advocate having no gas at all for a bit. I was curious to know:

• If there is a current GUE standard
• if it is just slightly different from instructor to instructor (but all verification steps are in there)
• or if it is not thought to be important as long as you verify the bottle by depth marking alone.

I know this is on the edge of being pedantic but I have never personally heard this one put to bed.

Cheers

Chris B

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graham_hk(Offline)

I suspect this is one of those things that is not too important as long as you get all of the important stuff. In Cave 2 (Last June) our instructors were happy with the following.

Signal team switch, Identify bottle (based on markings), deploy secondstage, left hand traces back along hose to bottle, turn on , purge and switch, team confirms bottle.

The one problem that I can see with George's method (and IIRC it was discussed on Quest some years ago) is the lack of a purge before breathing - thus anything in the reg is going to end up in your mouth. This was emphasized as an important step in Cave 2 when switching any reg.

Graham

Bart78660(Offline)

Pretty close to us except were taught this in Tech 1:

Check depth, Signal team switch, Individually Check depth, Identify bottle (based on markings), buddy confirms bottle, deploy second stage by tracing hand from sticker up to the 1st stage then pull hose out and never let go of the hose with your left hand - then grab second stage with right hand, left hand traces back along hose to bottle, turn on , turn off , purge and verify needle movement goes down, turn back on, check depth, switch, ok

This is done with your buddy watching you.

Regards,

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graham_hk(Offline)

yeap - missed the depth

we were told the needle drop was an extra check (belt and braces) and not necessarily necessary :D

Davey Willo(Offline)

Yep just about what we were taught too... I like to purge and see a needle drop before I start breathing the gas.

MonkSeal(Offline)

AFAIK we were taught turn on before pulling out hose. The rest was like you described.

carlson

IMHO

GI3's methode is in line with keeping ist simple.
But extra refinement/steps increase safty and task load.

If you take a very carefull first breath, be ready to "rinse and spit".

For diving in very cold water purging is not a very good idea (free flow).

David Martin(Offline)

Could this be an area where some variation is permitted (shock horror )?
Anyway, the place that I'd want a definate confirmation from the team that its OK to switch is just before turning the bottle on "properly" (as opposed to for the on/off/purge check). Up until this point you're not going to stick a live reg with a hot mix in your mouth.

You can also commence the other steps as you move up to a gas switch depth - since the reg isn't live, so that at the switch depth the regs are out, in your hand, everything that can be is checked but the reg is turned off....then confirm with the team to switch (which would be a confirmation that the bottle selected OK for the depth(confirmation with the reg deployed has the advantage that there's no chance for the something to happen, the switchee to be distracted and then select another bottle after the check) and that there's no other reason not to switch) and all switch.

This maximises what can be done concurrently/in advance reducing the delay between arriving at the switch depth and the last team member switching.

David

Davey Willo(Offline)

Well it's not really a 'purge' but more of a 'burp' and that's mainly to see the needle drop (confirming correct stage/reg IIRC..) plus the fact that the valve was still turned off would illiminate any freeflow issues anyway.

Once burped and needle dropped, then its turn valve on, pop it in and breath that bad boy..

At least that is what we were taught.

Rgds
Dave.

Clare Gledhill(Offline)

Shock horror - personal preference - whatever next....

Seems to be just one thing missing here - unless I missed it somewhere... which is possible - I do have to try to get some work done today

We start deployment when we leave the stop before, IDing bottles, tracing hoses, purging regs (bit harder to see the gague fall when wearing multiple bottles) and turning on.

All of this is done with the reg hose out in front of the diver, we only put the reg round our neck and start to breathe when signaled by a team member that we have hit the right depth and that they are satisfied that we are on the right gas.

This way a team of three can still switch within a few seconds of reaching the stop depth - having done all the preparation beforehand.

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