85m air dive

[Hammerhead]

Not trolling, but I don't understand that post. I had always under that "normoxic" referred to trimix with an O2 content of between 18% and 22%? Presumably that would be correct with the MOD which AJ had indicated in his post (18% O2 max MOD at 1.4 ppO2 is 223', if my maths is right)?

Not a trimix diver, but always keen to learn something new if I am missing something obvious.

No problem, I can be a bit obscure at times.

Anyway, I'm referring to ajduplessis' comment "21/40 is normoxic, not trimix. I also use 50% at 69ft and 100% at 20ft (both 1.6 PPO2)."

If it contains three gases, it's trimix, end of story; what he's describing is called "normoxic trimix" and if ajduplessis is a trimix certified diver without knowing this, then something is very, very wrong. Sorry, but I also vote troll.

 

[kittles]

I'm pretty new but my understanding is:

hypoxic (less than 21% o2), normoxic (21% o2), and hyperoxic (greater than 21% o2)
used to describe the oxygen levels in the gas?

trimix (3 gas mix, generally nitrogen, oxygen and helium), heliox/heliair (helium + o2), nitrox (nitrogen + o2 in a hyperoxic level)
used to describe for the most part, the number/types of gasses used?

So you can have normoxic trimix provided the o2 portion of the mix is 21% (or close to it), and you could have hypoxic trimix where the o2 portion is sub 21%?

That was how I understand it (I'm not multi-gas trained btw.. just observations)

 

[ajduplessis]

Ok I really should have said 260' as that is I dive I do often but I will give you the math for 300'

Bottom gas 12/60 I will use 160 cu ft. I will carry 300 cu ft.
First Deco gas 21/35 I will use 60 cu ft. I will carry 80 cu ft.
Next Deco gas will be 50/25 and I will use 40 cu ft. and carry 80 cu ft.
Last will be O2 I will need 33 cu ft. and carry 52 cu ft.

As for carrying that much gas I have seen more for a 427' wreck dive.

Thank you for the information. I will have feedback for you shortly (proposed setup, or eating my words...)

I assume the following? Please correct me if I am way of target?

Bottom gas 12/60 I will use 160 cu ft. I will carry 300 cu ft.
First Deco gas 21/35 I will use 60 cu ft. I will carry 80 cu ft. Switch around 200ft?
Next Deco gas will be 50/25 and I will use 40 cu ft. and carry 80 cu ft.Switch around 70ft
Last will be O2 I will need 33 cu ft. and carry 52 cu ft. Switch at 20ft

I assume you have all aluminium config

 

[ajduplessis]

No problem, I can be a bit obscure at times.

Anyway, I'm referring to ajduplessis' comment "21/40 is normoxic, not trimix. I also use 50% at 69ft and 100% at 20ft (both 1.6 PPO2)."

If it contains three gases, it's trimix, end of story; what he's describing is called "normoxic trimix" and if ajduplessis is a trimix certified diver without knowing this, then something is very, very wrong. Sorry, but I also vote troll.

Normoxic refers to to the content of O2. Yes, they both contain the same 3 gases, but normoxic have a depth limit. For me, this is the difference between normoxic and trimix, that is how I distinguish between the 2.

Secondly, I am not trimix certified, but normoxic (normocix trimix, before you have fit again). Something is seriously wrong if other non-trimix members understand what I tried to rely, but a commercial diver does not.

Keep going, son, you're special!!!!

 

[Kern]

I'm pretty new but my understanding is:

hypoxic (less than 21% o2), normoxic (21% o2), and hyperoxic (greater than 21% o2)
used to describe the oxygen levels in the gas?

trimix (3 gas mix, generally nitrogen, oxygen and helium), heliox/heliair (helium + o2), nitrox (nitrogen + o2 in a hyperoxic level)
used to describe for the most part, the number/types of gasses used?

So you can have normoxic trimix provided the o2 portion of the mix is 21% (or close to it), and you could have hypoxic trimix where the o2 portion is sub 21%?

That was how I understand it (I'm not multi-gas trained btw.. just observations)

We're divers, the usual convention is hypoxic & normoxic are trimix. Sure, air is normoxic, but it's just called air. Heliair would be air + He, also trimix. Hyperoxic could be EAN>21, but it could also be Trimix, eg. 30/30 (30% O₂/ 30% He/ 40% N₂), or 21/35, etc..

 

[Kern]

Thank you for the information. I will have feedback for you shortly (proposed setup, or eating my words...)

I assume the following? Please correct me if I am way of target?

Bottom gas 12/60 I will use 160 cu ft. I will carry 300 cu ft.
First Deco gas 21/35 I will use 60 cu ft. I will carry 80 cu ft. Switch around 200ft?
Next Deco gas will be 50/25 and I will use 40 cu ft. and carry 80 cu ft.Switch around 70ft
Last will be O2 I will need 33 cu ft. and carry 52 cu ft. Switch at 20ft

I assume you have all aluminium config

What do the switch depths have to do with balancing the rig? Why would you assume all the tanks are aluminium?

I would have assumed something like double steel 110ft³ back gas & an ali 80ft³ bottom stage, 2 ali 80ft³ & a 52ft³ deco stages.

Bugger going on this dive, my backs killing me just thinking about it, let alone the deco time.

EDIT. Just did some browsing, he's not using double steel 110ft³ back gas & an ali 80ft³ bottom stage, he's using, 130's filled to 4000 psi so they have about 300 cu ft of gas in them.

NEXT EDIT. Sorry all, just did some more browsing, there are photos & everything already, please ignore this useless post.

 

[Rhone Man]

hypoxic (less than 21% o2), normoxic (21% o2), and hyperoxic (greater than 21% o2) used to describe the oxygen levels in the gas?

That was sort of the point I was making above, except that my understanding was that "normoxic" includes a range of 18%-22%. Although that is not 'normal' in the sense of 'the same as air', it is richer than "hypoxic" which is the level at which you have to start considering the use of a travel gas. As I said, I'm not a trimix diver, but I am pretty sure I read that somewhere.

But I guess whatever label you give it, your mix is your mix.

 

[ScubaSteve]

But I guess whatever label you give it, your mix is your mix.

(this is just a response to your post and not directed at anything you said)

Agreed however this whole moronoxic discussion started because someone stated very clearly that trimix was not trimix. As long as the label you give is accurate in an open forum, then your mix is your mix. Otherwise what you post can be very dangerous or misleading (that individual's post falls into that category IMO). I too am not trimix certified but like the idea of people scrubbing information here so there is an obvious level of truth in it for those that can learn something (like myself).

 

[Tortuga68]

I... like the idea of people scrubbing information here so there is an obvious level of truth in it for those that can learn something (like myself).

 

[kittles]

We're divers, the usual convention is hypoxic & normoxic are trimix. Sure, air is normoxic, but it's just called air. Heliair would be air + He, also trimix. Hyperoxic could be EAN>21, but it could also be Trimix, eg. 30/30 (30% O₂/ 30% He/ 40% N₂), or 21/35, etc..

That's exactly my point.. the **oxic label is there to define o2 levels and has nothing to do with how many different gasses are blended in the mix. I'm sure people use the term in the wrong context and "mean" something else but that doesn't make it right

Comparing "trimix" to "normoxic" is like comparing apples to green. You can have a green apple and a red apple but at the end of the day it's still an apple.