Question Bailout gas configs for tech/deep chestmount rebreathers

[211ratsbud]

Is this why some practice DIL switching?

 

[justinthedeeps]

You'll be shocked to learn there's a whole universe out there diving 10/50 dil on every dive. With some variety of BO (not combo dil/BO)

ps I'm not in that sphere

I'm guessing the philosophy there is something like the 45+m END and 8g/L at 100 metres is just as fine as a little hypoxia now and then?

Just not the same without that "deep feeling" we had on those 50 metre air dives

 

[kensuf]

According to the internet that is a myth. My 7 of them were caused by me. Nothin to do with apeks and their service kits. I think Ken had more than my wife and I.
But I was the a-hole for saying why I despise apeks
I’ll take all the 30 year old mk25s that haven’t been serviced in 25 years over a new shiny apeks 1st all day.

I only had six.

 

[J-Vo]

One more thing about having a separate offboard hypoxic deep bailout is you can easily close that tank valve (after pressurizing) for your initial entry, plan an S-drill at ~10 metres where you re-open it and check the reg/BOV, and close it once again during deco stops, to eliminate any chances of accidentally breathing it above 10 metres.

10/70 is .2 at 10m. Why is there even a question if this is an issue?

 

[Wibble]

You should have a look at the standard gas table for deco mixes

You should have a look at the standard gas table for GUE deco mixes

FIFY

 

[justinthedeeps]

10/70 is .2 at 10m. Why is there even a question if this is an issue?

Do you not understand my sentences?

They describe shutting the hypoxic tank when you are shallower than 10 metres.

Are people with hypoxic twinsets doing this? Probably not?

 

[jale]

GUE’s position doesn’t affect mine. I’ve been critical of GUE for quite some time.

My apologies for the mix-up but how can you dare?

 

[Wibble]

someone mentioned it- 80% isnt as effective if needed to
a) offgas
b) feed your ccr if needed
c) provide a good gas if you haver a DCS problem

versus
making your gas cover a slightly wider range while carrying the disadvantages of abc

Big advantage of 80% is you can get high pressures == carry more gas. You may have a booster, but some don't or won't use it to boost to higher pressures.

There's very little difference in using 100% over 80% in deco times as 80% on 9m/30ft stop is on a good gas (PPOO2 = 1.52) compared with 50% (PPOO2 = 0.95)

80% doesn't need air breaks.

80% into CCR if O2 has failed isn't particularly poor unless its at extreme depth where the 20% N2 dilutes the He diluent.


It's all moot. Those that do do, those that don't don't.

 

[J-Vo]

Do you not understand my sentences?

They describe shutting the hypoxic tank when you are shallower than 10 metres.

Are people with hypoxic twinsets doing this? Probably not?

This "~" does not mean this "<". Please go back and look at your post.

I don't think shutting down your necklace reg is ever a good idea. Better to have hypoxic gas than no gas.

Even on OC taking "Air Breaks" with hypoxic back gas at the 10ft/3m stop has never been an issue for me. So I'm not too worried about squarting a little in my loop accidentally. That said, I've also never dove anything like 5/90. If I'm doing a dive that requires a mix like that, I hope to have a habitat.

 

[justinthedeeps]

don't think shutting down your necklace reg is ever a good idea. Better to have hypoxic gas than no gas.

I am talking about 10/70 specifically. I'm pretty sure this could lead to fatal blackouts at the surface, for anything more than a couple breaths.

This whole thread began that way ("Q: What's a good first rebreather? A: "Oh I like my chest mount for 100 metres")

And I am saying this a someone who even takes mini-breaths from hypoxic stages in predive checks to check that the regs work.

I am saying that with offboard hypoxic bailout cylinders, there is a very easy procedure to completely avoid breathing it near the surface. And yes I use it. On deco ascents, just close it and clip it off behind you, or get rid of it. You simply will not need that gas anymore.

What do the 10/70 backmount people do about having two active onboard regulators of surface-deadly gas around their necks? Nothing? I am guessing nothing.

However, I have not done the experiment myself. So I'm going to do something really rare around here and be open minded: go ahead and test this hypothesis, but please with someone there to apply oxygen if it doesn't work out. And not in the water.

If it turns out that you can switch to 10/70 for more than a a couple breaths while sitting on the couch or faffing about on the surface and it's fine, maybe then we're all wrong about what is hypoxic.

Lot of people are dead from hypoxia though.