OC Gas switch protocols?

[CptTightPants21]

I am not talking about starting a dive with 2 deco regs around your neck. I'm talking about starting with 1 and then asking about the possibility that you would somehow make the mistake of forgetting to stow it. Then, later, you do a switch that is supposed to be to your back gas, but you accidentally switch to that deco reg instead. Say, a buddy has some kind of emergency and you donate your long hose and switch to what you think is your alternate back gas reg.

I'm not asking you to teach me how to dive hypoxic mixes. I'm trying to understand the different ways people do gas switches and the pros and cons of them - which includes how they scale up to bigger dives. Obviously, it seems better to use a protocol from the beginning that will still work even on really big dives.

This specific question is really about whether you treat a switch to back gas exactly the same way as you treat a switch to a deco gas. Does your buddy verify that you switched to the correct gas (when you switch to back gas)? Does he literally view the entire length of the hose? Do you fully deploy the long hose so that you/your buddy can see the whole thing to verify that you are switching to back gas? Or do you assume that you would only have one deco reg around your neck, and if you're breathing from it, then the other regs around your neck MUST be back gas, so they are safe to switch to without verifying them the same way you verify a switch to deco gas?

This seems like it would particularly relevant if you happened to end up in low viz. If you forgot to stow your deco reg that you were using on initial descent, your buddy might not even be able to see you well enough to notice that you have that extra reg hanging there.

Y'all were talking about Jim Miller's death. What I got from your discussion was that he died because he switched to "back gas" (or so he thought) and neither he nor any of his buddies actually verified the gas he switched to. Did they all make that mistake because there is a mentality that switching to back gas doesn't need a verification? I understand that he switched to a bottle that wasn't a back mounted "main" cylinder. But, it still begs the question, is there a mentality that says "I only have to check switches to deco gases" that lead to that failure of process for him and his buddies. And is that appropriate? If not, should ALL switches, including to back gas, be treated exactly the same way? Or is this a case of teaching and continuing to teach "just don't be an idiot"?

1. "Back Gas" is only gas that is in your primary cylinders. You can be breathing from a bottle that has the same mix as your back gas, but then you are breathing from "the stage". Jim Miller didn't switch to back gas, he was breathing from a stage. I forget the exact situation, weather it was a support diver mix up or all Jim, but Jim's 70ft bottle was mixed up (switched) with his deep bottle and Jim ended up breathing from his 50% bottle for almost at hour before his convulsed.

2. Your primary reg will be clipped to your chest D-ring so that is one thing.

I have never seen or be trained to have any kind of verification for back gas, mostly because there is only 1 bottle deployed at once. If you are going off the deployed bottle, you are switching to back gas automatically, because that's the only possible reg choice (the other bottle is not deployed).

I am just having a hard time understanding the scenario you are picturing in your head.

 

[stuartv]

Your long hose is clipped off to your chest. You can't just leave a reg dangling around your neck. You're literally asking me to teach you the entire procedure from normoxic trimix all the way up to hypoxic trimix hot drop and every detail along the way. No, sorry. There's too many nuances and considerations that need to be assessed for a dive like that. If we aren't even on the same page about something as simple as what do to between deco gases there's no way we can really have a meaningful discussion about what to do when you make a 200fpm descent to 270' and what to do along the way..

Okay. I'll take that. I think you've taken my questions as disagreeing with you. That happens a lot and is rarely actually the case. I ask those kinds of questions to really understand what YOU think - not just me assuming what your reasoning is.

FWIW, you have me pretty well convinced that switching to back gas between deco gases makes sense. That's a bonus for me, since that's how my tech instructor here teaches it. When I'm taking a class, I do whatever the subject is the way I'm being taught. But, it definitely makes me feel better if I have learned as much as I can about it and what I'm being taught jibes with what I have tried to learn on my own.

Anyway, thanks for taking the time to explain what you have.

 

[PfcAJ]

Okay. I'll take that. I think you've taken my questions as disagreeing with you. That happens a lot and is rarely actually the case. I ask those kinds of questions to really understand what YOU think - not just me assuming what your reasoning is.

FWIW, you have me pretty well convinced that switching to back gas between deco gases makes sense. That's a bonus for me, since that's how my tech instructor here teaches it. When I'm taking a class, I do whatever the subject is the way I'm being taught. But, it definitely makes me feel better if I have learned as much as I can about it and what I'm being taught jibes with what I have tried to learn on my own.

Anyway, thanks for taking the time to explain what you have.

Nah I don't think you disagree, and if you did I wouldn't mind. But you're asking me to detail out every step and I just can't do that for you.

 

[stuartv]

I have never seen or be trained to have any kind of verification for back gas, mostly because there is only 1 bottle deployed at once. If you are going off the deployed bottle, you are switching to back gas automatically, because that's the only possible reg choice (the other bottle is not deployed).

I am just having a hard time understanding the scenario you are picturing in your head.

It's clear (to me, now) that there are at least 2 solid schools of thought on the gas switch protocol. And, I believe both teach a process that is safe.

The point is that, sure, there's only 1 bottle deployed at once. There's only 1 reg choice. Etc.. It's all fine ... when you actually do what you were trained to do. But, people seem to vary from how they were trained. Sometimes, shockingly easily.

My hypothetical scenario where things would not all be "fine" is because someone made a mistake and failed to do what they were trained to do. In the example, I wasn't even supposing that they did it on purpose or consciously. I'm saying what if they end up with an extra deco reg around their neck because shtuff happened and they got interrupted and forgot to stow that deco reg. I have certainly forgotten to clip off my main reg on occasion, when I was supposed to. I have seen people, in the benign conditions of the people, forget to stow their deco reg after they were done with it. Or forget to turn their deco bottle off after they were done with it, or whatever.

It just doesn't seem like that much of a stretch to imagine that someone might, at some point, have something happen where they switch to back gas and forget to stow the deco reg/hose they were using, then end up with it hanging around their neck for a while. And once you're there, then any later protocol that ASSUMES you would never make that mistake becomes suspect and subject to scrutiny.

Anyway, I think I'm good on this subject for now. I'm happy to continue to talk about it, but I don't want to make people feel like I'm beating a dead horse....

 

[PfcAJ]

It's clear (to me, now) that there are at least 2 solid schools of thought on the gas switch protocol. And, I believe both teach a process that is safe.

The point is that, sure, there's only 1 bottle deployed at once. There's only 1 reg choice. Etc.. It's all fine ... when you actually do what you were trained to do. But, people seem to vary from how they were trained. Sometimes, shockingly easily.

My hypothetical scenario where things would not all be "fine" is because someone made a mistake and failed to do what they were trained to do. In the example, I wasn't even supposing that they did it on purpose or consciously. I'm saying what if they end up with an extra deco reg around their neck because shtuff happened and they got interrupted and forgot to stow that deco reg. I have certainly forgotten to clip off my main reg on occasion, when I was supposed to. I have seen people, in the benign conditions of the people, forget to stow their deco reg after they were done with it. Or forget to turn their deco bottle off after they were done with it, or whatever.

It just doesn't seem like that much of a stretch to imagine that someone might, at some point, have something happen where they switch to back gas and forget to stow the deco reg/hose they were using, then end up with it hanging around their neck for a while. And once you're there, then any later protocol that ASSUMES you would never make that mistake becomes suspect and subject to scrutiny.

Anyway, I think I'm good on this subject for now. I'm happy to continue to talk about it, but I don't want to make people feel like I'm beating a dead horse....

I agree that people can deviate from what the plan is. Imo this is where a buddy is very helpful. They are another set of eyes on you and what you're doing. If they see that you've goofed they can correct you, and you can correct them.

Working together stops a small goof from becoming a big problem.

 

[tbone1004]

It's just weak procedure. Doesn't scale, has potential to break down if you have to borrow a reg, and is generally just lazy.

All you have to do is move your eyeballs to look at your buddy. It's seriously easy. Some dumb **** might go down like inhaling a rock, switching to a dead reg or a stage, or something that's just a minor annoyance like a hose gets jammed up by the boltsnap. You're unable to lend a hand because it's too hard to look at your buddy?

I can't even relate to this.

we all dive solo regularly so it scales better than having to change procedure when we dive together. If you don't have a buddy, who are you going to look at to verify anything? the wall? If you don't dive solo you certainly wouldn't be able to relate to this, but if you do dive solo, or your buddy gets lost, or dies, then you have to find what works for that situation because a dead or nonexistent buddy can't verify anything. We have found what works for us when we solo dive, and prefer not to change when we dive together.
I don't rely on the regulator being different because it doesn't change the validation that my tank is marked properly and is my tank, it just adds extra verification that it is what I think it is. If I borrow regulators it doesn't change anything in the procedure because it's still
validate the tank is the right tank
verify the regulator you think is attached to that tank is attached to that tank
inhale exhale, repeat as necessary

 

[Kevrumbo]

I learned it as switch to your deco gas (or the next higher FiO2 deco gas) coming off from your backgas in OC diving. Common example, in a Nitrox50 to Oxygen Switch, the intermediary step would be switching from Nitrox50 to backgas and stowing the Nitrox50 deco reg; then ascending to 6m/20' breathing the backgas, and then finally switching from backgas to O2. . . (Or a deeper example, Triox 35/25 to a 50/25 switch, the intermediary step would be switching from 35/25 to backgas and stowing the 35/25 deco reg; then ascending to 21m/70' breathing backgas, and then finally switching from backgas to 50/25). . .

The only time where you might have to consider optionally switching directly from Nitrox50 to Oxygen at 6m, is if you have a extreme hypoxic OC backgas mix like Trimix 10/70.

 

[JohnnyC]

Let's say stage, 2 deco gases (50 & O2), and backgas.

When stage is dusted, signal to watch you switch. Unclip long hose, purge, and switch.
Stage reg gets stowed, nose clipped to hip, ascend to first deco stop.

Signal to watch switch, confirm depth and MOD, you and your buddy. Deploy deco hose, purge, trace hose, blah blah all the procedural stuff, confirm depth again, switch to reg, clip off back gas. Deco and ascend as per usual.

End of 9m stop, switch to back gas as above. Stow 50 deco reg. Kick O2 off leash. Unclip 50 from chest, clip to leash. Transfer O2 from leash to left shoulder, re-stow leash behind you. Ascend to 6m.

At 6m, switch to O2 from back gas as per same protocol, Depth, MOD, etc. Deco, then surface.

If you don't like to nose clip or carry O2 on a leash, the procedure is all the same, just less transferring of cylinders.

You never have more than the deco/stage reg and your back gas around your neck. If you're too task loaded to stow your deco reg, you're not in any position to perform a gas switch. Every switch should be observed and confirmed by your buddy. If you don't have a buddy, no big deal, you should be as diligent in your procedure regardless of another set of eyes.

 

[ajduplessis]

I think Icd is one of those textbook risks that doesn't really happen in real life.

Not sure Don Sherley is going to agree with your statement.

 

[lv2dive]

Not to speak for AJ but the (not-insignificant number) divers I know, who are now (or have been in the past) doing regular dives to 200-300' feet aren't worried about ICD until the dive is going to hit 300-350' (opinion varies on the which depth one should start planning for it).

I do think it is safe to say dives to depths deeper than 300' feet are not the territory of the average tech diver, and planning for those types of dives should be covered as part of a a good tech class as well as conversations with other more experienced divers along the way.

Not sure Don Sherley is going to agree with your statement.