Gas Switching Protocols

[Flightlead]

Interested in understanding and comparing pros and cons of the gas switching protocols taught by various agencies.

DSAT teaches the NO TOX mnemonic:
N - Name - Is this my tank?
O - Observe the MOD marking and current depth - can I breath this mix?
T- Turn on the valve
O - Orient the regulator - ie deploy reg/hose make ready to exchange
X - Exchange and examine - switch regs and examine your team mates to ensure they are breathing a correct mix

What are others teaching?

 

[rjack321]

depth
select tank (mod)
trace+deploy hose/reg
turn on tank
confirm (mod+reg) with buddy
flip hose over head and switch
depth
cleanup any messiness

I don't get what the my vs. your tank achieves

 

[Steve SDI/TDI HQ]

What I teach...

Suggested Procedure for Gas Switching during Decompression Diving Doppler’s Blog

 

[battles2a5]

My procedure is the same as Steve's, with one exception; Once I turn a gas on I hold it at arms length and purge to verify I have the right second stage instead of breathing it down. The reason I do this is to ensure that the reg has been cleared if there was any flashing in the valve or reg. As long as you store your bottles "off", you are still ensuring that you have the correct reg, and minimize the chances or breathing fire or some nasty byproducts thereof. My cave instructor told me some horror stories that prompted me to add this to my procedure.

Another point I would add is that if you switch from one deco gas to another, switch to bag gas first, then stow the first gas and turn it off before deploying the next gas. This way, there is only one deco reg routed behind your neck, only one deco gas that is on, and you further reduce the odds of breathing the wrong gas.

 

[Flightlead]

depth
select tank (mod)
trace+deploy hose/reg
turn on tank
confirm (mod+reg) with buddy
flip hose over head and switch
depth
cleanup any messiness

I don't get what the my vs. your tank achieves

regarding the "n" as in Name on Tank its really more of a double check that you really picked up the tank you intended to. Although at that point in the dive its a bit moot. and frankly, if the MOD is correct go ahead and breath it. from my perspective, if I've been so careless that I picked up the wrong tank on the dock/boat whatever and only notice it at the switch perhaps I'm in the wrong hobby

maybe they came up with a cool mnemonic and needed an "n"

 

[Flightlead]

What I teach...

Suggested Procedure for Gas Switching during Decompression Diving DopplerÃÔ Blog

I like the visual check of the SPG change once breathing the tank as a second double check that the reg is connected to the tank you think it is. with all the confusion of hoses if you are carrying multiple tanks that is a good check. although if you are keeping all your deco bottle valves off unless being used - which I think we all do - you'll know pretty quickly if you aren't breathing what you think you are.

I notice your labeling guidelines are for 2 labels on each side. perhaps its overkill, but I label mine in 5 places - with MOD only. smaller label on opposite sides at the top of each tank, one facing me and one facing my team mate when we are in position facing each other. one each side of the tank in large numerals, and one on the bottom to be visible to someone behind you.

 

[Flightlead]

Another point I would add is that if you switch from one deco gas to another, switch to bag gas first, then stow the first gas and turn it off before deploying the next gas. This way, there is only one deco reg routed behind your neck, only one deco gas that is on, and you further reduce the odds of breathing the wrong gas.

do you build in any time to do this?

 

[JeffG]

do you build in any time to do this?

Our team never did. We considered it kinda a "back-gas" break.

 

[battles2a5]

I usually add 1 min to each gas-switch stop, more if it is with a team of 3 or with people I haven't done a big dive with before. In practice, it takes me less than 30 seconds or so to complete the switch and get everything where it needs to be, but a couple of extra minutes RT is not that bid a deal and you can be sure everyone is squared away.

 

[rjack321]

do you build in any time to do this?

For me... Normally the last stop of a gas (e.g. 30ft for 50%) is done on backgas. There is little benefit to a deco gas at that portion in its usage and the break serves to both reset your O2 clocking a little and provide a time to stow the old deco reg before deploying the new at the next stop. Its not necessary to double this stop to "stay on deco schedule". Then again, my deco probably has less time at 30ft on 50% than most.

ps thank for the reminder about purging. I do that too, just forget all about it in the retelling.