Do main tanks reg swaps (L/R) involve a gas-verification protocol in technical sidemount?

[MichaelMc]

In technical sidemount, when changing between the regs for the left and right main (back/bottom gas) tanks, is there a gas-verification protocol such as used when going to a different gas in technical diving? In terms of knowing what gas you are breathing. Such as: checking depth, tank, tracing reg, involving buddy?

I ask in the context of looking ahead to using stage or deco bottles.

In backmount, except ID, we do not accustom ourselves to switching between regs without verifying. Except..., for switching to the necklace in need or when swapping back to the long hose after an OOG drill or necklace reg check.

In sidemount we do change back and forth between L/R main tanks several times during the dive. Does acquiring this habit of not tracing our main tank regs when we change regulators become a concern once we have other regs with unbreathable gases.

One of my diving safety officers, a technical and below 400' CCR scientific diver, raised the question as a possible concern. I'm not looking to critique sidemount protocol, rather to understand the technical one.

My impression from the board is that for rec. sidemount one just changes regs. I have not seen any discussion that this is a habit one needs to be broken of, for your main L/R tanks, once you start carrying unbreathable gases. I just wanted to check that impression.

Thanks.

ETA 1:
I know main L/R sidemount tanks have the same gas; I am not advocating changing that. Also, I'm fluent at the task of swapping between my left and right tank second stages to keep the tanks balanced, have a reserve in each and exit on the tank I want to.

The question is if lots of unverified (equal gas) second stage changes between main sidemount L/R tanks is viewed as adding a risk, of habituation to changing regs without checking what gas the reg was attached to. A risk when different gases in other tanks are then added to the diver. Understanding that reg-gas-verification (gas switch) procedure would be used for the different gassed tanks, but perhaps still not between the main (same gassed) tanks.

 

[Manatee Diver]

Would be interesting to hear the answers from the non-cave context, as I've briefly discussed this in a cave context where stages almost always have the same gas as your "back gas."

 

[girlwithbigtanks]

Sidemount tanks are treated the same as backgas backmount tanks. Deco tanks and stage tanks are the treated same whether backmount or sidemount.(ie proper gas switch procedures) Sidemount we just keep our tanks volume balanced, especially on overhead dives. I would never use different gas in my primary/bottom gas Sidemount tanks. That’s just dumb.

 

[ScubaWithTurk]

There is no gas switch protocol because you are not switching gasses. All you are doings is switching cylinders. The long hose is clipped off when not in use and the short hose (if using a bungee config) is around the neck. The deco gases have regs that are stowed away so there is no possible way to mistake your bottom gas for your deco gas.

The bottom gas is verified when gearing up. These cylinders go on the top and the second stages are put into place as stated above. . Once verified, the deco cylinders get attached below these cylinders with second stages stowed away. This means there is no reason to trace a reg unless you are switching to a deco gas.

 

[MichaelMc]

I changed many instances of 'gas-switch' to 'gas-verification' in the OP and the title. To help focus the question.

Yes, main L/R (back/bottom gas) second stage swaps are not a gas switch, when that is what actually happens.

The concern was that the second stage swaps are 'pick a second stage off the body or gear and put it in the mouth.' Is there a concern for being habituated to doing that without verifying what gas it is, once some second stages on the body/gear are a different gas?

@ScubaWithTurk suggests that the (main) L/R bottom/deep second stages being necklaced or clipped off makes a difference.

 

[ScubaWithTurk]

When one switches to a deco gas, at this time you can cleanup back gas hoses. I know some who leave the bungee on and stow the longhose. I prefer this way of doing things. Now I only have two gases with second stages that are free. One is bungeed around my neck and is my known bottom gas (in case I need to quickly get back on that gas) and the other is the deco gas which would be verified by myself and my team prior to breathing off it.

I do suggest the bottom deco gases having the hoses stored makes a difference as there is no way I will grab one of those by accident when doing a normal reg swap.

 

[MichaelMc]

When one switches to a deco gas, at this time you can cleanup back gas hoses. I know some who leave the bungee on and stow the longhose. I prefer this way of doing things. Now I only have two gases with second stages that are free. One is bungeed around my neck and is my known bottom gas (in case I need to quickly get back on that gas) and the other is the deco gas which would be verified by myself and my team prior to breathing off it.

I do suggest the bottom deco gases having the hoses stored makes a difference as there is no way I will grab one of those by accident when doing a normal reg swap.

I think part of my DSO's question might be this. Say you have gone to deco and stowed your long hose on the tank. But then you go back to your deep gas necklace, as you say. What do you do with your deco second stage? Do you clip it off to the right chest? Let it hang from the neck? Restow it, amid whatever caused you to switch back to the necklace? Take it off the neck and clip to the left chest? The first two are places you are accustomed to switching to without gas verification and it is now not breathable at all depths.

I have not taken deco procedures, so I do not know how ingrained procedures are for what to do with a rich gas second stage that is leaving your mouth.

(A deco second stage hanging from the neck could also happen in backmount in this scenario. Though clipping it off to the right would likely result in two regs clipped off, which could raise flags if they were reached for and you found both of them.)

(I'm not doing scientific diving in sidemount, so my DSO's question, about habituation to unverified second stage swaps, is just a general reservation of his about sidemount.)

 

[wstorms]

For me, it's quite easy; left main gas is on the necklace, right main gas on the longhose. Those are easy to identify and switch to whenever needed. When switching to deco, do a proper gas switch procedure. Now there are two options:
- switch back to main gas: no verification needed when switching to necklace, minor validation when switching to the longhose (trace the longhose a bit)
- switch to another deco cylinder / gas. Switch back to main gas first (as above), clean up the used stage. proper gas switch procedure to the new deco stage

The only scenario that I can think of where this might not work is when using hypoxic trimix as a main gas at a really shallow depth. In that case you might not be able to switch back to main gas. On the other hand, I do not know any hypoxic OC sidemount divers....

 

[ScubaWithTurk]

. On the other hand, I do not know any hypoxic OC sidemount divers....

Very true! Normoxic is about the limit for OC sidemount at lest as far as I am concerned. Anything further is CCR and more often that not, normoxic dives would also be on the rebreather.

 

[Subcooled]

I keep my sidemount cylinders (bottom gas) open all the time as regulator switches are frequent. The deco cylinders (one or two) are closed but pressurised. Besides, bottom gas regs I carry on a neck bungee (pick your preferred way of keeping them available) while deco/stage regs are stowed away during transport. The only check I do is to keep bottom gas cylinder pressures close to each other, as was told in a previous post. Gas switches I do just like in backmount... There are several reasons to keep deco/stage cylinders closed but regs pressurised including but not limited to avoiding unintended gas switches.