why a 32 mix standard?

[Soggy]

"(minimum FO2 to maintain consciousness at 1 ATA)"

Which is normally considered to be in the area of 16%.

Yes, thank you for repeating exactly what I said....

 

[yceltikci]

And can please tell me the idea behind using TMx for decompression at 36 m. for example? GUE's standart mixes offer 35/25 for deco gas around 36 m.s. This calculates to an END of 13.5 m.

Can we elaborate on this?

Regards,
Yener

 

[cmalinowski]

Originally Posted by cudachaser
At 1.6 pp O2 132 is the max 32%

and I love the fact that I understand what you are saying here. I just finished my Nitrox class. I love knowledge.

Michael

But try and understand more about what DIR-Atlanta and Lamont are saying because 1.6 is not our (DIR Diver's) max PPO2 for diving; 1.4 is. 1.6 is decompression PPO2. 1.2 is working PPO2. A 1.4PPO2 for 32% is 111. So, 100' is not a "hard deck" but is is the "cushiony bottom" we like

OxTox is anything but understood. Like decompression sickness, we can't be sure if shaking a dead chicken over you before the dive will improve or hinder your chances of being hit by either. DCS is usually survivable. OxTox underwater is less likely survivable. Thus, that one (PPO2) becomes a real driving factor on mixes. Because it's not like you hit 1.6 and you'll tox. It may be more (1.8, 1.9, 2.0), but it may be less...

Plus, for us simpletons, the math is pretty easy

Chris

 

[mwhities]

But try and understand more about what DIR-Atlanta and Lamont are saying because 1.6 is not our (DIR Diver's) max PPO2 for diving; 1.4 is. 1.6 is decompression PPO2. 1.2 is working PPO2. A 1.4PPO2 for 32% is 111. So, 100' is not a "hard deck" but is is the "cushiony bottom" we like

Chris

I believe I'm understanding that. 1.4PPO2 is my max anyway one looks at it. That's what I was trained with and that's where I am staying. Unless my future training says something else.

Thanks for giving me a heads up on that.

Michael

 

[Soggy]

And can please tell me the idea behind using TMx for decompression at 36 m. for example? GUE's standart mixes offer 35/25 for deco gas around 36 m.s. This calculates to an END of 13.5 m.

Can we elaborate on this?

Regards,
Yener

Not sure I understand the question. 35/25 is the 3rd deco gas, used at 120ft. It would take a pretty enormous dive to require this gas, but when it is, that's what would be used. The first two gases would be 50% (70ft) and 100% (20ft). The deco gases are chosen to make the switch to the next gas before the PO2 gets too low to be useful for decompression and to avoid potential ICD issues while still keeping a reasonable END.

 

[rainman_02]

And it has to do with rock bottom to your first gas switch...otherwise the bottom gas + reserves requirement gets really huge!

 

[limeyx]

"(minimum FO2 to maintain consciousness at 1 ATA)"

Which is normally considered to be in the area of 16%.

I have yet to meet a diver who considers 21-18% to be hypoxic.

it can depend on the conditions.
If you are in rough seas with big doubles, AL80 stage, 2 deco bottles and a video camera and are exerting yourself, maybe 18% can become hypoxic.

However, if you are in calm conditions, you might find 16% is fine.

I have not had an issue with 18% and never dove 16%.

And I guess according to the literal definition with 21% being normoxic (what we normally breathe on surface), anything less can be considered hypoxic.

 

[cmalinowski]

And can please tell me the idea behind using TMx for decompression at 36 m. for example? GUE's standart mixes offer 35/25 for deco gas around 36 m.s. This calculates to an END of 13.5 m.

Can we elaborate on this?

Regards,
Yener

END of 13.5m?

END = (1-FHe)*ATA
END = (1-.25) * 4.6
END = (.75) * 4.6
END = 3.45a
END = 24.5m
END = 80'

O2 is considered as narcotic, or more so depending on your school, as N2.

Since it is a deco gas, the PPO2 max of 1.6 = 35% O2 @ 36m

Chris

 

[yceltikci]

Hi,

I have no problem with using Hyperoxic gas for the deco. But why TMx? It is much more expensive and we do not need TMx for 36 m.s... Do we? Why not EAN35 instead of TMx 35/25

What I was telling here was if we use Trimix 35/25 at depth 36 m. then we will have an END of 13.5 m.

Why do we need a gas which gives us END=13.5.

I'm OK with high O2 percentage, which helps for shorter deco durations.

Regards,
Yener

 

[Soggy]

I have no problem with using Hyperoxic gas for the deco. But why TMx? It is much more expensive and we do not need TMx for 36 m.s... Do we? Why not EAN35 instead of TMx 35/25

Helium serves multiple purposes here...

35% has a MOD of 117, which is below the maximum 100ft (and recommended 80ft) END.

Additionally, switching from a 15/55, 12/60, or 10/70 to 35/0 would cause a huge N2 slam and introduce isobaric counter diffusion issues. At these depths, it is likely that someone would consider putting more than 25% helium in that gas and *also* put 15-25% helium into their 50% gas to ease themselves off the helium.