Timing of preparatory gas switch actions (not actual gas switch)

[divezonescuba]

I have had the good fortune to receive excellent technical training at various levels from four different well known technical instructors. One of the things that I noticed is that there seems to be differences in the preparation phase of a gas switch.

I am not talking about the actual gas switch, but the preparatory actions. These include identifying the correct bottle, tracing the hose, cracking and closing the valve, purging the reg and observing the pressure gauge, opening the valve, positioning the hose, repurging the valve, and the checking others. Obviously you will check your depth at the switch stop to confirm the safe depth regardless of when you do the preparatory steps.

So the question is, assuming no current or a drift deco, at what point do you do these preparatory steps prior to the actual switch at the correct depth. Seems like there are advantages and disadvantages to each way.

 

[northernone]

Here's a little to get discussion going.

I might fiddle with hoses prior to reaching my switch depth, but my final check immediately before a reg goes in my mouth is to trace it's origin and read the mix. I won't prepare minutes before with the added time leaving the possibility of me getting confused.

I have dove with some teams where it's "if you're not on the deco gas when you reach switch depth, you're wasting your teams time and endangering them" in those situations I prep on the ascent and double check the gas and hose routing at the switch depth. It does faster the second time and presumably any significant issues have already been dealt with the first time. When with less time pressed teams (or more frequently solo), I do my gas prep at the switch depth.

All in all I want to know what I'm breathing.

Regards,
Cameron

 

[tbone1004]

*warning, very non-kosher gas switch*

I switch to long hose if in sidemount as I'm approaching the bottle.
I grab the bottle, check to make sure it's the right bottle, open the valve, check pressure
Pull the second stage out and hang it over my neck
Don bottle

At this point, I know that I have long hose in my mouth, short hose on the necklace, and the "free" second stage is the bottle I just picked up.
I don't open valve, close valve, purge, open valve. I have never really seen that much benefit in it when you are tracing the hoses. I also dive Poseidons which are quite violent when purging.

I then verify depth, switch regs, clip off long hose, and switch computer. Assuming I'm at depth, it takes less than 30 seconds since I'm donning a bottle

I typically drop bottles off at or real close to the depth they're supposed to be since it's in a cave so I don't really have any "transition time". In really depends on where bottles are and what not. Deep stuff where the first stop is at 70ft? Sure, any bottom stages get stowed, the 70ft bottle comes out, will go through the validation checks like above because there isn't anything else to do, and in a cave all the stage bottles get nose clipped before I grab the next bottle, usually on the way to that bottle.

I don't do buddy gas switch checks unless I have a buddy that wants to do that. One of my buddies is active with GUE and when we cave dive we have always gone with solo-style gas switches.

If I'm carrying the bottle for any length of time before the switch, I unclip the bottom, swing it forward and do the same procedure just have the top end clipped in already

similar to above, if I have a dive buddy that has strong feelings about how to do a gas switch, I'll play by those rules. Doesn't really bother me, but that's what I do when solo or with my normal buddies

 

[victorzamora]

I might fiddle with hoses prior to reaching my switch depth, but my final check immediately before a reg goes in my mouth is to trace it's origin and read the mix. I won't prepare minutes before with the added time leaving the possibility of me getting confused.

I see nothing wrong with doing all of the "work" for the gas switch just prior to actually getting to stop depth. I stow all stages and clean up as much as I can before donning my deco bottle.

I think that what you said is crucial: final check immediately before breathing off of it. Before any gas switch, I trace the hose to the valve to confirm it's the bottle I want before breathing it.

 

[PfcAJ]

Not doing a buddy check is straight up laziness and stroke nonsense. Too much work to move your eyeballs?

Get some discipline.

 

[tbone1004]

Not doing a buddy check is straight up laziness and stroke nonsense. Too much work to move your eyeballs?

Get some discipline.

Regularly dive solo and all of my procedures are set up for solo diving.
With my regular buddies, the dynamic is that we are same ocean diving and happen to be diving together. Very different dynamic that diving in a "team"

That said we do eye each other, but it's not the formal "flash, look at me, gas switch, *touch bottle markings*, OK, OK, switch" and do them one at a time. Everyone is expected to be able to handle themselves and we are there as a convenience more than anything. We have seen no sense in putting extra procedures in that can't be done when you are solo diving. Is it an added safety buffer? obviously, but not one compatible with solo diving....

 

[LiteHedded]

If you’re diving with a buddy, may as well go ahead and make sure he has switched to an appropriate gas. His loved ones will thank you if you stop him from becoming a body recovery. One of the biggest killers in technical diving. Blows my mind people dive this way

 

[tbone1004]

If you’re diving with a buddy, may as well go ahead and make sure he has switched to an appropriate gas. His loved ones will thank you if you stop him from becoming a body recovery. One of the biggest killers in technical diving. Blows my mind people dive this way

Don’t disagree but to what extend are we talking? Is it a full formal procedure or a quick glance before you arrive at the bottle since we all have big mod stickers on the bottoms?
I pay attention to those on approach and glance over during my switch procedure sure but don’t consider that a buddy check. I associate that with verification from the buddy that it’s the right bottle before you switch and unless asked to do that in pre dive it’s not something that I choose to do and my regular buddies have never asked for it

 

[jeffmg]

I stow my light in the temp position and tuck the cord maybe 10 feet before the stop

But pulling the hose before getting situated at switch depth, checking depth then checking bottle markings and mod sticker in that order seems to ask for trouble

Focusing on one step of the process at a time is a way to keep things slow and smooth

Slow is smooth, smooth is fast

 

[TrimixToo]

At the bottom, or max depth, I verify deco gas valves are off. At the prior stop, or on the way to the stop with the first switch, I reverify all deco tanks off. Then I turn on the first one. On reaching the stop, I locate the tank by MOD, unship the valve, follow the hose back to the tank, recheck the MOD, and put the reg in my mouth. If I get more than two breaths from a deco reg, it's the right gas. 2nd switch (and, rarely, 3rd) are the same, but without the assurance of having the other valves off; I leave the valves on all breathable mixes open as I ascend.

The recheck by MOD following the hose saved my butt the day I clipped off the deco bottles on the wrong sides. I was so surprised the tanks were on the wrong sides that I checked again! But pure O2 at 70' would not have ended well that day.

Like tbone, I am more often solo than not. Even more rarely have I got an OC buddy.