DIR- Generic Tdi Normoxic trimix or CCR?

[LanceRiley]

Well spotted. Ten years in a couple of weeks

Am well aware of the DIR wars and GI3's missives also the change in stance about 7 years ago. Had a dalliance with GUE in the beginning of my career.

As previously said, the principles of DIR has done so much for diver safety and standards, certainly compared with the wild-west of decades ago.

Whilst DIR evolved from cave diving, it's the wider world that has adopted much of its concepts. Longhose, standard gases, kit configuration.

The challenge now is the brave new world of helium rationing; the old standards simply cannot be used -- nobody's going to dive 21/35 for a 35m/115ft dive on open circuit. If you're *truly* wedded to DIR then you would never dive without standard gasses. Even if they're adapted, for example 25/25 down to 45m/150ft, it's still not viable on open circuit.

And here we are back at the nub of the matter. Our OP wants to dive deep and needs a way forwards. Either it's back to Causteau's day and deep air (please don't), or it's CCR.

Just for one moment accept that the only true DIR-compliant rebreather is a GUE JJ. How will you ever get to use that if you have to be T2 qualified in an environment without helium?

Practically this means the route to CCR for our OP is not GUE, but is TDI, IANTD and all the other agencies who are running the manufacturer-specific MOD1 (which allows helium) and MOD2 classes (which adds long deco within bailout constraints).

I have considered tdi ccr on a JJ. You see… im not interested in scuba politics. More on the depth i need to achieve to see some wrecks before theyre gone.

 

[LanceRiley]

That’s what the OP is certified to do today. Air to 45 meters. That’s the traditional progression, right? Intro to tech then AN/DP which then allows the diver to dive air to 45 meters. Whereas GUE has fundies then tech 1 which allows divers to dive to 50 meters on 18/45.

My point is, the argument folks are advancing against trimix sooner rather than later is all around either cost or convenience. I dunno. Sounds like nickel rocketry to me. Never does anyone profer an argument that states that the other way is better. That it is safer. That it builds a better diver. Only that it is cheaper.

Tdi exteded range is air up to 55m

 

[PfcAJ]

Alternatively, your gas mixologist pulls his phone out of his back pocket, enters the parameters -- current gas & pressure, target gas & pressure -- then boosts in whatever's available.

Few places outside of Cave Country bank helium. Have never found a place anywhere that banks and doesn't do partial blending.

Again, the technology has moved on. We have gas mixing programs (apps) available to all.

I mix my own fills from my three twinset banking cylinders. Because I am filling 3 litre steel cylinders, it's very easy. I just need my gas dealer to occasionally (cave) fill the bank cylinders. I'll get 10 or more dives out of a fresh set for dives down to 70m/230ft (e.g. 15/55). It's like paying for one open circuit dive and I get 10 or more.

I tend to mix standard gasses for my dives as it’s easier to remember the MOD for them (although with CCR you don’t use 1.4 PPO2 for diluent, you aim for lower 1.1 in case you need to do a dil flush)

“Few places bank helium”

Yeah. I know. I just told you what you can do in places that don’t. 32% is super common and banked everywhere. If your shop doesn’t do helium, it’s mad easy to put He in your tanks at home/ your storage unit or whatever and then get them topped with 32% at the shop.

If everywhere banked helium gases and the world was full of trimix-equipped dive shops, we wouldn’t even be talking about this. Everyone knows about gas mixing apps on their phones…. Not everyone knows about the helium and 32% relationship for standard gases.

 

[Whitrzac]

“Few places bank helium”

Yeah. I know. I just told you what you can do in places that don’t. 32% is super common and banked everywhere. If your shop doesn’t do helium, it’s mad easy to put He in your tanks at home/ your storage unit or whatever and then get them topped with 32% at the shop.

If everywhere banked helium gases and the world was full of trimix-equipped dive shops, we wouldn’t even be talking about this. Everyone knows about gas mixing apps on their phones…. Not everyone knows about the helium and 32% relationship for standard gases.

Out of the 6 or so shops within a 3hr drive from me. None of them bank 32% ether...

 

[Wibble]

32% is super common and banked everywhere. If your shop doesn’t do helium, it’s mad easy to put He in your tanks at home/ your storage unit or whatever and then get them topped with 32% at the shop.

You mean 21% is super common and available everywhere.

Banked mixes aren't at all common unless you only dive in Cave Country; maybe a few other high-volume locations such as holiday resorts as they use membrane compressors and need to run them for a while.

 

[crofrog]

You mean 21% is super common and available everywhere.

i've not found anywhere in the US where you can not get banked 32% (although some northeast shops bank 40% and then top with air), I've never had a problem finding banked nitrox in mexico either. For instance I'm in baltimore maryland, and there are at least 3 shops I can get banked 32% at inside a 45 minute drive, and trust me when I say there is no good diving around here. Just some quarrys and the bay with mud and 2-4ft of vis...

Figuring out the logistics before you get where you're going is just part of it.

You don't need a membrane to bank nitrox either, you can do continuous blending.

 

[Marie13]

i've not found anywhere in the US where you can not get banked 32% (although some northeast shops bank 40% and then top with air), I've never had a problem finding banked nitrox in mexico either. For instance I'm in baltimore maryland, and there are at least 3 shops I can get banked 32% at inside a 45 minute drive, and trust me when I say there is no good diving around here. Just some quarrys and the bay with mud and 2-4ft of vis...

Figuring out the logistics before you get where you're going is just part of it.

You don't need a membrane to bank nitrox either, you can do continuous blending.

Many areas have what I refer to as “warm water shops.” They do very little local diving, mostly just for training, and promote the crap out of multiple warm water trips a year. Those places aren’t going to bank nitrox. They’re probably not going to offer anything but air fills. A number of the Chicago area shops are like that.

Major metro areas are probably going to have at least a couple shops that offer nitrox fills, but it’s a crapshoot if they bank or not.

 

[elgoog]

Many areas have what I refer to as “warm water shops.” They do very little local diving, mostly just for training, and promote the crap out of multiple warm water trips a year. Those places aren’t going to bank nitrox. They’re probably not going to offer anything but air fills. A number of the Chicago area shops are like that.

Major metro areas are probably going to have at least a couple shops that offer nitrox fills, but it’s a crapshoot if they bank or not.

These aren't your target shops for technical diving services though. A shop that doesn't cater much to local diving and/or only does air fills is not a valid comparison in this context. Leave aside helium, we're not even going to get oxygen for our deco gas mixes here.

Banked mixes are just a convenience in that the shop might fill your tanks while you wait. If you use @PfcAJ 's method of filling a tank with helium to a certain pressure and taking it to a shop, they can use whatever combination of their air, 32%, oxygen to get you the mix you want. Ready 32% just removes any gas mix calculations.

 

[Wibble]

These aren't your target shops for technical diving services though. A shop that doesn't cater much to local diving and/or only does air fills is not a valid comparison in this context. Leave aside helium, we're not even going to get oxygen for our deco gas mixes here.

Banked mixes are just a convenience in that the shop might fill your tanks while you wait. If you use @PfcAJ 's method of filling a tank with helium to a certain pressure and taking it to a shop, they can use whatever combination of their air, 32%, oxygen to get you the mix you want. Ready 32% just removes any gas mix calculations.

Recreational shops may be the only gas shops nearby and you have to work within your means.

Typically those recreational shops do not have booster pumps either, HP oxygen only available following a new delivery. Obviously they cannot do high pressure 100% either -- 50%, 32% generally no problem using partial pressure blending.

As I understand it, America's a big place so finding a tech gas shop might require many hours of travelling. Will probably use multiple cylinders for the journey,. Or just invest in your own compressor and booster $$$$$

 

[wetb4igetinthewater]

In the past gue divers who were certified for tech 2 dives did a training which was almost the same as ccr 1.

That makes me super curious about GUE's CCR1 course, as my TDI CCR mod 1 (air dil) was so dramatically different than my TDI trimix (normoxic) course. While my current rebreather is the Prism 2, with all the extra weight needed for excess air space, it is pretty darn heavy. My instructor switched over to a Meg which is more dense and overall lighter according to him (please don't dog pile on me if this is incorrect/I misunderstood him). But that's a switch I will do much later.