Gas switches - multiple deco gasses

[AndyNZ]

I guess really a Tech 2 question, but I'm interested in knowing the process for switching between multiple deco gasses.

My best guess is this:

Leanest mix is carried on the outside to make it accessible
Ascend to first switch depth, prep first deco tank, switch regs, clip off back gas reg
Ascend to second switch depth (and this is where I'm unsure of what would be best)

-> Unclip backgas and switch to it <- ???

Stow first deco mix reg, unclip tank and swap position with second deco mix
Prep second deco tank, switch regs, clip off back gas reg


Any comments welcomed, thanks in advance.

 

[JeffG]

We always went to backgas first, cleanup the used deco tank and then got ready for the next deco tank.

 

[rjack321]

#1 Position of the tank (inside, outside etc) is NOT use to ID it, only the MOD stickers are used for that.

Otherwise yes, you switch to your long hose for a lean mix break at the last stop of a gas before switching to the next gas 10ft shallow. All but the most extremely O2 lean mixes are breathable at 30ft.

so e.g.
120ft switch to 35/25
stops in here...
80ft switch to backgas stow used stage reg
70ft switch to 50%
stops in here...
30ft switch to backgas stow used stage reg
20ft switch to O2
ascent

Switching from a stage to a stage is a CF.

 

[Bismark]

I guess really a Tech 2 question, but I'm interested in knowing the process for switching between multiple deco gasses.



Stow first deco mix reg, unclip tank and swap position with second deco mix
Prep second deco tank, switch regs, clip off back gas reg


Any comments welcomed, thanks in advance.

Not necessary to move deco gases if only carrying two bottles on your side and no leash. By this stage of the game you should be able to do gas switches from inside and outside bottles. 40" hose works for both. There are some different considerations when using a bottom stage and two deco bottles and moving the bottles around, but you didn't ask that question.

Ask yourself what switching bottle positions brings to the party. Upside, maybe slightly more convenient doing gas switch with bottle on top. Downside, losing deco bottle............oops............don't create a potential problem when you don't need to. Like Richard says, bottle position is not used to verify bottle contents anyways so for two deco gases and backgas only, dance with the lady that brung ya.........verify MOD with team and that is the deco gas you use. I try to arrange my bottles on the surface, but this is really more of an issue with 80's and 40's mixed together than with say two 40's.

 

[AndyNZ]

#1 Position of the tank (inside, outside etc) is NOT use to ID it, only the MOD stickers are used for that.

Yeah, thanks... but presumably it is carried outermost on the stack for convenience and the checked prior to breathing from it?

During switching tank positions, is the first tank generally clipped off on the hip d-ring, or are tanks swapped just by holding them?

 

[JeffG]

Yeah, thanks... but presumably it is carried outermost on the stack for convenience and the checked prior to breathing from it?

During switching tank positions, is the first tank generally clipped off on the hip d-ring, or are tanks swapped just by holding them?

Which one is outermost? Regardless of which one is "outer" vs "inner" makes one tank easier to read and the other "harder" Since you have multiple switchs...the end result means it doesn't matter.

For the ordering of tanks, I arrange the tanks so that the ones that get used last are on top. That way they (the tanks) hold down the tanks used...but this only makes a big difference when one of the tanks is a stage.

Swap tanks with using a lease. There should only ever be one tank that isn't a) clipped to yourself or b) the leash.

 

[AndyNZ]

Not necessary to move deco gases if only carrying two bottles on your side and no leash. By this stage of the game you should be able to do gas switches from inside and outside bottles. 40" hose works for both. There are some different considerations when using a bottom stage and two deco bottles and moving the bottles around, but you didn't ask that question.

Ask yourself what switching bottle positions brings to the party. Upside, maybe slightly more convenient doing gas switch with bottle on top. Downside, losing deco bottle............oops............don't create a potential problem when you don't need to. Like Richard says, bottle position is not used to verify bottle contents anyways so for two deco gases and backgas only, dance with the lady that brung ya.........verify MOD with team and that is the deco gas you use. I try to arrange my bottles on the surface, but this is really more of an issue with 80's and 40's mixed together than with say two 40's.

Thanks - very useful. I'm coming at this from having in a previous life done left and right mounting of deco tanks.

I've done some playing around in the pool with left mounted multiple deco tanks, and am trying to work out the best way of doing it - the swapping tanks around did seem a little onerous for just two tanks. Back to the pool for more practice.

 

[rjack321]

Yeah, thanks... but presumably it is carried outermost on the stack for convenience and the checked prior to breathing from it?

During switching tank positions, is the first tank generally clipped off on the hip d-ring, or are tanks swapped just by holding them?

You would only switch to a cylinder clipped on your left side (chest and hip)

Unused cylinders (maybe empty, maybe full) go on a leash on your hip. There is a protocol for bringing them forward is that what you want to know? I honestly don't think you want to try and learn that protocol on the internets.

 

[AndyNZ]

Unused cylinders (maybe empty, maybe full) go on a leash on your hip. There is a protocol for bringing them forward is that what you want to know? I honestly don't think you want to try and learn that protocol on the internets.

I think this is mostly for dealing with 3 or more tanks, yes?

Not in my area of interest right now - maybe in a few years time. I had it in my head that you should swap the position of two tanks around, but this has been cleared up.

 

[JeffG]

I think this is mostly for dealing with 3 or more tanks, yes?

Yes. Stage plus 2 or 3 deco gases. Too much for 1 arm pit to handle