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Why 50% ?

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Why 50% ?

Post Number:#1  Postby Nizaha » Wed Sep 26, 2007 10:09 am

Hey gangs

Here my question?

Why would you choose 50% vs. 100% in a single deco bottle situation?

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Zaha
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Re: Why 50% ?

Post Number:#2  Postby Mephisto the Heretic » Wed Sep 26, 2007 5:50 pm

tembak yee (ballpark) .......depth limitation regarding PP which leads to O2 tox?
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Re: Why 50% ?

Post Number:#3  Postby Nizaha » Wed Sep 26, 2007 9:38 pm

mephistophelies wrote:tembak yee (ballpark) .......depth limitation regarding PP which leads to O2 tox?



Let say if you diving with 30% back gas to 40 mtr, which deco mix do you prefer memphisto? 50% or 100% ?

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Re: Why 50% ?

Post Number:#4  Postby dp » Wed Sep 26, 2007 10:45 pm

At the risk of being "whacked" (hehe), i would choose 50%.

50% has a higher MOD (deeper than 100%), hence letting me off gas at different depths while doing the deep stops.


Do correct me if i am wrong, pls.

(I have yet to do the extended range course..  :P).
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Re: Why 50% ?

Post Number:#5  Postby Mephisto the Heretic » Thu Sep 27, 2007 12:38 am

Nizaha wrote:
mephistophelies wrote:tembak yee (ballpark) .......depth limitation regarding PP which leads to O2 tox?



Let say if you diving with 30% back gas to 40 mtr, which deco mix do you prefer memphisto? 50% or 100% ?

Zaha


ok beb. this is a bit beyond me. but let me try. bear with me. not tech certified, not even nitrox but want to understand.can aaa?

first please explain definition and function:

1. Back gas
2. Deco mix
Last edited by Anonymous on Thu Sep 27, 2007 12:40 am, edited 1 time in total.
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Re: Why 50% ?

Post Number:#6  Postby Nizaha » Thu Sep 27, 2007 1:40 am

Backgas mean what percentace O2  inside your double or single tank during the dives. (primary gas)
Ex:  32 % O2 with 1.4 PPO2 = 34Mtr
And Deco mix is the tank you sling around your left side or right side depend on training organization. I'm normally sling 2 stage on both left side with percentage of O2 .

At least you interested with this subject. That's fine Memphisto.

Other  reason why 50% O2 deco mix most popular mix is in case you miss the 6mtr stop like bad condition etc wave or blow up the last stop. Earlier off-gasing is better for you. Also remove the N2 from your blood sooner and bubbling down.

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Re: Why 50% ?

Post Number:#7  Postby John F SeaDemon » Thu Sep 27, 2007 2:38 am

Good topic Zaha.

May I add here: back gas means the primary gas you use to conduct the dive. Deco mix would be the ones you use to help off gas on ascent.

50% as explained by Zaha allows for early off-gassing. Another reason is if you lose your 100% O2 and you still have a lot of 50% mix left, you can use your 50% as a substitute to your lost 100% O2 and just double the deco times at 6m and 3m. 50% is the easiest to calculate.
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Re: Why 50% ?

Post Number:#8  Postby Nizaha » Thu Sep 27, 2007 2:53 am

SeaDemon wrote:Good topic Zaha.

May I add here: back gas means the primary gas you use to conduct the dive. Deco mix would be the ones you use to help off gas on ascent.

50% as explained by Zaha allows for early off-gassing. Another reason is if you lose your 100% O2 and you still have a lot of 50% mix left, you can use your 50% as a substitute to your lost 100% O2 and just double the deco times at 6m and 3m. 50% is the easiest to calculate.



Right on.. thanks SD..
Travel gas : Also allowed you breathing certain mix from point A to point B( this will applied with deep trimix dives)
Zaha
Last edited by Nizaha on Thu Sep 27, 2007 3:01 am, edited 1 time in total.
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Re: Why 50% ?

Post Number:#9  Postby joe » Thu Sep 27, 2007 8:15 am

SeaDemon wrote:Good topic Zaha.

May I add here: back gas means the primary gas you use to conduct the dive. Deco mix would be the ones you use to help off gas on ascent.

50% as explained by Zaha allows for early off-gassing. Another reason is if you lose your 100% O2 and you still have a lot of 50% mix left, you can use your 50% as a substitute to your lost 100% O2 and just double the deco times at 6m and 3m. 50% is the easiest to calculate.


err..means that 50% for ascent and another 50% for descent?
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Re: Why 50% ?

Post Number:#10  Postby Sicko » Thu Sep 27, 2007 8:28 am

Anyone using 80%? Apart from the 2 popular deco mixes?
Anyone can do a dive to 100m or more.....
But how many will return alive???
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Re: Why 50% ?

Post Number:#11  Postby Nizaha » Thu Sep 27, 2007 9:44 am

joe wrote:
SeaDemon wrote:Good topic Zaha.

May I add here: back gas means the primary gas you use to conduct the dive. Deco mix would be the ones you use to help off gas on ascent.

50% as explained by Zaha allows for early off-gassing. Another reason is if you lose your 100% O2 and you still have a lot of 50% mix left, you can use your 50% as a substitute to your lost 100% O2 and just double the deco times at 6m and 3m. 50% is the easiest to calculate.


err..means that 50% for ascent and another 50% for descent?


I'm not sure what you mean but We're not talking about the rules of third or gas planning here. I think you might get confuse here.anyways we never drain our tank!

50% O2 mix never changes at any depth but eventually will changes if you changing new tank !!! only partial pressure of O2 will changes at depth !

I hope this will help

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Zaha
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Re: Why 50% ?

Post Number:#12  Postby Nizaha » Thu Sep 27, 2007 9:46 am

Sicko wrote:Anyone using 80%? Apart from the 2 popular deco mixes?


I think 2nd most popular deco mix is 100% O2. that what I learn during my class. Not much between 80% or 100%. might changes the Deco obligation.

Zaha
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Re: Why 50% ?

Post Number:#13  Postby John F SeaDemon » Thu Sep 27, 2007 10:50 am

Nizaha wrote:
Sicko wrote:Anyone using 80%? Apart from the 2 popular deco mixes?


I think 2nd most popular deco mix is 100% O2. that what I learn during my class. Not much between 80% or 100%. might changes the Deco obligation.

Zaha


I agree.

I know some tech divers rationalise that using 80% for the last stops is safer than using 100%, but my preference would be 100% so I can off-gas quicker. Like I mentioned above. If it gets risky to do 100% (surge conditions beneath the surface) I will pop in my 50% and double the calculations.
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