OC Gas switch protocols?

[boulderjohn]

@boulderjohn What agency did you train with that had the most elaborate gas switch protocols?

UTD

 

[boulderjohn]

In my training, each diver on a team was supposed to do the following upon arrival at the appropriate depth for a switch.

1. Signal to a buddy asking that buddy to watch while you performed the switch.
2. Show the buddy the MOD label on the bottle to which you are planning to switch.
3. Watch as the buddy checks the depth gauge and then gives the OK.
4. Pull out the hose and drape it over the neck.
5. Look at the SPG to make sure the tank is still pressurized. If not, pressurize it.
6. Purge the regulator while looking at the gauge to make sure the pressure dropped while purging, indicating that you do indeed have the correct bottle.
7. Open the valve.
8. Begin breathing.
9. Exchange OKs with the buddy watching you.

After that, your buddy would go through that process. If you are in a team of 3, each of the 3 would go through the process in succession. As I said, in dives outside of training, that never happened.

 

[stuartv]

UTD

And, per your earlier post, even that one did not involve switching to back gas between deco gases.

BTW, I watched a video by AG on how to do a gas switch. It was definitely a bit more elaborate than how I was trained. But, the differences seemed pretty small, really. And the video did not address changing from one deco gas to another, so I didn't know how he/UTD trains for that.

 

[boulderjohn]

. And the video did not address changing from one deco gas to another, so I didn't know how he/UTD trains for that.

And I can't say I do, either. When I left them, I was only certified for one deco gas, although we could and did carry and use stages.

 

[stuartv]

In my training, each diver on a team was supposed to do the following upon arrival at the appropriate depth for a switch.

...
After that, your buddy would go through that process. If you are in a team of 3, each of the 3 would go through the process in succession. As I said, in dives outside of training, that never happened.

Which part(s) usually didn't happen?

My training was mostly the same except did not include watching the SPG while purging (but I have only had training, so far, for 1 deco bottle). And in my training, one person is designated as the Deco Captain, who directs all the switches. For a team of 3, the DC can have both team members doing their switches at the same time. Whoever finishes first would then typically do their part for observing the DC as the DC then does their own switch.

 

[PfcAJ]

I don't recall ever being on a dive where we didn't verify each other's deco gas switches.

It's pretty important.

 

[boulderjohn]

Which part(s) usually didn't happen?
.

I don't recall ever being on a dive where we didn't verify each other's deco gas switches.

It's pretty important.
.

It's very important.

The main thing that went immediately was the one at a time aspect. Soon everyone pretty much had their deco regs ready to go by the time we reached the stop depth. After that, procedures varied. That's the problem--procedures varied after the switch. The original steps described above did not include a serious post-switch examination because of the elaborate pre-switch processes, which are the ones that got skipped.

What I see in most people today is actually a two step process. Each individual on a team simultaneously selects the bottle and makes the switch, after which each person carefully checks teammates to make sure that each one made the correct switch. The more elaborate procedure seems to me to be based on the assumption that full verification by a teammate must be made before the switch begins, an assumption that seems to be based on the belief that a toxing event can happen within the first 20 seconds on the wrong gas. If you instead assume that nothing bad is going to happen in those first few seconds, you can focus on making a good examination of your teammates after the switch.

 

[PfcAJ]

It's very important.

The main thing that went immediately was the one at a time aspect. Soon everyone pretty much had their deco regs ready to go by the time we reached the stop depth. After that, procedures varied. That's the problem--procedures varied after the switch. The original steps described above did not include a serious post-switch examination because of the elaborate pre-switch processes, which are the ones that got skipped.

What I see in most people today is actually a two step process. Each individual on a team simultaneously selects the bottle and makes the switch, after which each person carefully checks teammates to make sure that each one made the correct switch. The more elaborate procedure seems to me to be based on the assumption that full verification by a teammate must be made before the switch begins, an assumption that seems to be based on the belief that a toxing event can happen within the first 20 seconds on the wrong gas. If you instead assume that nothing bad is going to happen in those first few seconds, you can focus on making a good examination of your teammates after the switch.

We typically hold the reg out and wait for a confirmation before making the physical switch. Each diver *can* do all their steps independently then the buddy does a cross check against depth and bottle marking. It's fast and efficient without sacrificing anything.

The classroom version you describe is to teach the steps. The meat and potatoes is for the individual to check mod, depth, confirm the reg in your hand is attached to the right bottle, and buddy verifies.

 

[kensuf]

In my training, each diver on a team was supposed to do the following upon arrival at the appropriate depth for a switch.

1. Signal to a buddy asking that buddy to watch while you performed the switch.
2. Show the buddy the MOD label on the bottle to which you are planning to switch.
3. Watch as the buddy checks the depth gauge and then gives the OK.
4. Pull out the hose and drape it over the neck.
5. Look at the SPG to make sure the tank is still pressurized. If not, pressurize it.
6. Purge the regulator while looking at the gauge to make sure the pressure dropped while purging, indicating that you do indeed have the correct bottle.
7. Open the valve.
8. Begin breathing.
9. Exchange OKs with the buddy watching you.

After that, your buddy would go through that process. If you are in a team of 3, each of the 3 would go through the process in succession. As I said, in dives outside of training, that never happened.

I teach that same protocol, except #6 is breathe, not purge. I teach that through TDI, IANTD, and NAUI.

 

[stuartv]

I don't recall ever being on a dive where we didn't verify each other's deco gas switches.

It's pretty important.

I'm thinking now about the story (just told casually one day) my tech instructor told about how it went when he was doing his own Adv Trimix cert checkout dives. He described the start of the dive as a hot drop to hit a deep wreck. I remember him saying how they had to switch to their bottom gas as they dropped like rocks towards the bottom, having to stow the hoses and regs from their initial gas as they went. He didn't say one way or another but looking back, the way he described it makes me think that they did not do a formal gas switch (ala the way I have been trained) as part of that. Maybe they did. But, playing the scene in my mind based on how he described it, I imagine 3 divers (an instructor and 2 students) dropping as fast as possible and each one simply switching to back gas/long hose and stowing their reg/hose from one of their deco bottles as soon as they got past 30 feet (or whatever depth they chose).

If you don't do buddy checks/gas confirmation for that switch, what other gas switches do you eventually start doing without a buddy check/gas confirmation? Or is a switch to back gas always okay without that same formal gas switch/check/confirmation process?

When you switch from a deco gas to back gas, prior to then switching to the next deco gas, do you do the same process for the gas switch as when you switch to a deco gas? To what length do you/your buddy go to confirm that the reg you're switching to really is coming from your back gas? What if you had a mistake in an earlier stage and you still have a deco reg hanging around your neck, so you accidentally switch to that? What if it's during a descent and you are accidentally switching to a rich travel gas when you are supposed to be switching to your back gas?

To be clear, I'm not trying to criticize at all. I'm trying to understand what you all, as more experienced folks, actually do to mitigate various potential risks versus things that may seem risky to me but you have learned really aren't risks to be concerned about.