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Max Depth 23m - What gas you would choose?

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Max Depth 23m - What gas you would choose?

Post Number:#1  Postby Snafu » Fri Mar 16, 2007 10:05 am

Max depth 23m, average depth 16-18m  & you be doing 3-4 dives a day.

2D 1N diving trip & might do 1 night dive.

What type of gas is good for the dive?
- Work the gas out in here

Why would you choose that gas?
- I would like to know the advantage
- I would like to know the dis-advantage


* You only allowed to choose from 21% Oxygen & up to 40% Oxygen
* Dont worry on making mistake, better here then underwater

;D
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Re: Max Depth 23m - What gas you would choose?

Post Number:#2  Postby evo5555 » Fri Mar 16, 2007 10:32 am

Nazim kecil and Mocha, apamacam?hehee

No chart or wheel to refer to now as im in the office, but with this max depth and average depth, if possible go for EAN36.  Dont have, use EAN32 also best.

Advantage-less fatigue, short SI, and increased bottom time(stay long UW and no deco time  much much more than 21%)

Disadvantage:have to pay for the gas...hehe
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Re: Max Depth 23m - What gas you would choose?

Post Number:#3  Postby John F SeaDemon » Fri Mar 16, 2007 11:21 am

Hahaha..I'll leave this to your students, Snafu.  I expect to see their replies before the end of the day.
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Re: Max Depth 23m - What gas you would choose?

Post Number:#4  Postby Snafu » Fri Mar 16, 2007 11:33 am

Everyone can join  ::) the fun!!!!!

;D
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Re: Max Depth 23m - What gas you would choose?

Post Number:#5  Postby Jim » Fri Mar 16, 2007 11:38 am

Nazim kecil and Mocha, apamacam?hehee

No chart or wheel to refer to now as im in the office, but with this max depth and average depth, if possible go for EAN36.  Dont have, use EAN32 also best.

Advantage-less fatigue, short SI, and increased bottom time(stay long UW and no deco time  much much more than 21%)

Disadvantage:have to pay for the gas...hehe




Wei Evo...the question ask for the best gas mix. No need to refer chart or wheel. Just take out the calculator & punch in the figures. If forget how, hv to do refresher course with sifu. This time no spagetthi.... only rotan......

;D ;D ;D
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Re: Max Depth 23m - What gas you would choose?

Post Number:#6  Postby John F SeaDemon » Fri Mar 16, 2007 11:52 am

Nazim kecil and Mocha, apamacam?hehee

No chart or wheel to refer to now as im in the office, but with this max depth and average depth, if possible go for EAN36.  Dont have, use EAN32 also best.

[highlight]Advantage-less fatigue, short SI, and increased bottom time(stay long UW and no deco time  much much more than 21%)[/highlight]

Disadvantage:have to pay for the gas...hehe



Evo...this is a misconception. Using Nitrox does not mean you will have a longer time underwater. That all depends on your consumption rate. If you use up a 12L tank in 1 hour, you'll still finish up a 12L tank filled with whatever Nitrox mix in 1 hour.  What Nitrox gives you as an advantage is a longer time at depth: meaning, more advantageous especially if you are a photographer...you have longer time at depth as example given of 23m than those breathing compressed air.

Check your pressure T again to find out your best mix for this dive.
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Re: Max Depth 23m - What gas you would choose?

Post Number:#7  Postby evo5555 » Fri Mar 16, 2007 3:16 pm

Nazim kecil and Mocha, apamacam?hehee

No chart or wheel to refer to now as im in the office, but with this max depth and average depth, if possible go for EAN36.  Dont have, use EAN32 also best.

[highlight]Advantage-less fatigue, short SI, and increased bottom time(stay long UW and no deco time  much much more than 21%)[/highlight]

Disadvantage:have to pay for the gas...hehe



Evo...this is a misconception. Using Nitrox does not mean you will have a longer time underwater. That all depends on your consumption rate. If you use up a 12L tank in 1 hour, you'll still finish up a 12L tank filled with whatever Nitrox mix in 1 hour.  What Nitrox gives you as an advantage is a longer time at depth: meaning, more advantageous especially if you are a photographer...you have longer time at depth as example given of 23m than those breathing compressed air.

Check your pressure T again to find out your best mix for this dive.


SD, this is no misconception.  No mattter how many % O2 u have in the tank, capacity of 1 tank is still the same.  Its just what the gas can do for you at depth, or in other words, it takes longer time for you to hit the "dark side" of the table when u use EANx as compared to EAN21 hehe...sorry for the wrong expression in the earlier reply. Sifu taught us well  ;D
Last edited by evo5555 on Fri Mar 16, 2007 3:24 pm, edited 1 time in total.
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Re: Max Depth 23m - What gas you would choose?

Post Number:#8  Postby evo5555 » Fri Mar 16, 2007 3:21 pm

Nazim kecil and Mocha, apamacam?hehee

No chart or wheel to refer to now as im in the office, but with this max depth and average depth, if possible go for EAN36.  Dont have, use EAN32 also best.

Advantage-less fatigue, short SI, and increased bottom time(stay long UW and no deco time  much much more than 21%)

Disadvantage:have to pay for the gas...hehe




Wei Evo...the question ask for the best gas mix. No need to refer chart or wheel. Just take out the calculator & punch in the figures. If forget how, hv to do refresher course with sifu. This time no spagetthi.... only rotan......

;D ;D ;D


hahaha...Eh the i wrote the gas mix mah....hehehe...If got chart mayb can draw draw graph maybe?hehehe...Anwyay as for best mix, normally i will always stick to EAN32, as it provides the most flexible depth(max30m).  Who knows when u are diving u saw something exciting and wanan go deeper?hehehe..If you use EAN36 it will limit your depth again....
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Re: Max Depth 23m - What gas you would choose?

Post Number:#9  Postby BubbleBeaver » Fri Mar 16, 2007 4:05 pm

I have no experience with Nitrox whatsoever.  :( So at the risk of making myself look really dumb, I say I would choose EAN36. Is there a price difference between EAN32 and EAN36 (stupid question)? EAN36 max working depth is 29m, so given the max depth and average depths given by Snafu, it seems you won't have to worry bout the O2 toxicity factor. If the intention was to do a total of about 9 dives in less than 48 hours, I'd want the least amount of residual nitrogen in my body.

Ok did i just make a complete fool of myself?  ;) ;) :P
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Re: Max Depth 23m - What gas you would choose?

Post Number:#10  Postby John F SeaDemon » Fri Mar 16, 2007 4:16 pm

and increased bottom time(stay long UW and no deco time  much much more than 21%)[/highlight]


Evo, this is the misconception I was pointing at: Increased Bottom Time, and stay long UW.  Your correction on the matter is correct. Yes, your sifu has taught you well.

I know there are recreational divers who have this misconception, thinking that Nitrox gives you longer bottom time, and that you will never deco.

What is correct is longer time at depth, instead of stay long UW. You pointed out correctly 1 tank is 1 tank..whether it is compressed air, nitrox, or cooking gas. But being able to stay long UW is not correct. But staying longer at depth is correct.

The following examples employ the square profile, without coming up to do a safety stop, and assuming it is your first dive of the trip:

Example 1

12L tank with 20 Bar pressure and a SAC rate of 15 L per minute will give you 160 minutes on the surface. Regardless of what is inside the tank. At 30 meters it will allow you to stay at depth for 40 minutes.

Example 2

At 23 meters, the same tank will allow you to stay down at that depth for 48 minutes before finishing off the tank, again, regardless of what is inside the tank.

However,

Breathing compressed air at 23 meters will allow you to stay at depth for about 45 minutes (check your RDP to see if this figure is correct).  Breathing EAN40 at that depth (23 meters) gives you an Equivalent Air Depth of roughly 16 meters, therefore your non-decompression limit for that depth is roughly 72 minutes.

So, while your maximum allowable bottom time at depth is only 72 minutes (non-deco limit...so there is a deco time and penalty..if you venture beyond this limit), you can only stay down there for 48 minutes. That is your bottom time...regardless of the mix.  Why? Because the tank will run out of your EAN40 at 48 minutes.

So Nitrox does NOT give you extra time down there..nor will it allow you to stay underwater longer than when using compressed air.  It doesn't. Therefore it is a misconception. I would recommend divers to take up Nitrox course like Evo, Mocha and Sheik did and you will have a better understanding of the benefits of Nitrox diving.  The three guys I mentioned are THE technical divers: using mixes other than normal air as their back/travel gas. I only use it as a decompression gas  ;D
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Re: Max Depth 23m - What gas you would choose?

Post Number:#11  Postby John F SeaDemon » Fri Mar 16, 2007 4:40 pm

If Snafu will allow me (since he has said everyone can join the fun), I'll go on to explain a bit further. Tech divers can help me out and correct me if I am wrong.

For a maximum depth of 23 meters (as pointed out by Snafu), the mix allowable to this depth as its MOD is EAN42.  But since we're talking about recreational Nitrox, the best mix would be EAN40 (PPO2 of 1.32). Since 23m is the max depth, there is no risk of O2 Tox here. Using this mix at the average depth of 16m-18m gives tremendous benefits.  The disadvantage would be the increased exposure to CNS toxicity. With a PPO2 of 1.32, your max exposure in a single dive is 150 minutes; and total allowed in 24 hours is 180 minutes. So if you want to do 4 dives a day, you can only do 45 minutes each dive whether or not your tank's content can allow you to stay more than an hour each dive.

An excess of CNS toxicity will give you major trouble. It is better to be narced with Nitrogen than to have CNS toxicity. This who have gone for Nitrox course would remember your CONVENTID.  If you recognise these symptoms, then you should know what to do as it would still be in the pre-tonic build-up stage. If you go into tonic stage, you will be completely rigid and stop breathing. Any attempt to take you shallower as one would do in the event of N2 Narc, would give you barotrauma.

If you convulse, you will be unconscious until breathing restarts. Underwater, however, the chances of drowning is high. If you recover you may have post-convulsive depression...and breathe heavily to up to half an hour.

In a conscious recovery situation, you may suffer from amnesia, exhaustion, lethargy and confusion.

So in this case of diving EAN40 at 23 meters, you are limited to 4 X 45-minute dives per day.  To make the most of it, dive using this mix at 10 meters maximum. You can have 10 X 45-minute dives per day  ;D ;D ;D
Last edited by Anonymous on Fri Mar 16, 2007 4:41 pm, edited 1 time in total.
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Re: Max Depth 23m - What gas you would choose?

Post Number:#12  Postby John F SeaDemon » Fri Mar 16, 2007 5:16 pm

I have no experience with Nitrox whatsoever.  :( So at the risk of making myself look really dumb, I say I would choose EAN36. Is there a price difference between EAN32 and EAN36 (stupid question)? EAN36 max working depth is 29m, so given the max depth and average depths given by Snafu, it seems you won't have to worry bout the O2 toxicity factor. If the intention was to do a total of about 9 dives in less than 48 hours, I'd want the least amount of residual nitrogen in my body.

Ok did i just make a complete fool of myself?  ;) ;) :P


Nope...it's a safe choice.

But diving Nitrox your least worries is about residual nitrogen. You'd worry more about CNS toxicity.
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Re: Max Depth 23m - What gas you would choose?

Post Number:#13  Postby mocha » Fri Mar 16, 2007 7:31 pm

thanx SD... u just answered everything for me.... ;) hehehe
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Re: Max Depth 23m - What gas you would choose?

Post Number:#14  Postby John F SeaDemon » Fri Mar 16, 2007 7:55 pm

Nazim kecil and Mocha, apamacam?hehee


Nazimkecik in Perhentian already...hehehehe...long before he could be asked to answer this question.
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Re: Max Depth 23m - What gas you would choose?

Post Number:#15  Postby Sicko » Mon Jun 04, 2007 4:09 pm

Max depth 23m, average depth 16-18m  & you be doing 3-4 dives a day.

2D 1N diving trip & might do 1 night dive.

What type of gas is good for the dive?
- Work the gas out in here

Why would you choose that gas?
- I would like to know the advantage
- I would like to know the dis-advantage


* You only allowed to choose from 21% Oxygen & up to 40% Oxygen
* Dont worry on making mistake, better here then underwater

;D

3 to 4 dives per day..........
Air will do..........Nitrox costs extra & serve no practical advantage(For single tank, recreation dives)
Anyone can do a dive to 100m or more.....
But how many will return alive???
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Re: Max Depth 23m - What gas you would choose?

Post Number:#16  Postby John F SeaDemon » Mon Jun 04, 2007 9:25 pm

Max depth 23m, average depth 16-18m  & you be doing 3-4 dives a day.

2D 1N diving trip & might do 1 night dive.

What type of gas is good for the dive?
- Work the gas out in here

Why would you choose that gas?
- I would like to know the advantage
- I would like to know the dis-advantage


* You only allowed to choose from 21% Oxygen & up to 40% Oxygen
* Dont worry on making mistake, better here then underwater

;D

3 to 4 dives per day..........
Air will do..........Nitrox costs extra & serve no practical advantage(For single tank, recreation dives)


Hahaha..yes, Sicko. Thank you. Good to see you here finally. Hope you can do an intro of yourself in the Introduction thread.
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Re: Max Depth 23m - What gas you would choose?

Post Number:#17  Postby shafi » Mon Sep 24, 2007 11:58 pm

Max depth 23m, average depth 16-18m  & you be doing 3-4 dives a day.


Hmm, looks like our dive profiles the last trip in Redang Kalong, SD! And we were on plain ol' air..

I'm admitting I'm not (yet) a nitrox diver... (but I got the t-shirt  :icon_tongue: , so I am determined to get the certification before i dive in Bali in November). My concern actually is not merely on body fatigue, but residual nitrogen.

On the issue of EANx, with the max number of dives and minimum SI over 2 days, is that enough to affect your central nervous system? Or does this happen over a period of days/months? Weighing it out, then i'd agree with SD that it would be better narc then convulse. Of course, with proper planning and guidance from wise experienced ones will help us avoid both scenarios.

If the question is rhetorical, pardon the inexperience... but I have heard of nasty CNS toxicity and I am glad my two best buddies have decided to op out of one mad-a@s deep trip next month!

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Re: Max Depth 23m - What gas you would choose?

Post Number:#18  Postby Snafu » Thu Sep 27, 2007 11:31 pm

Shafi,

Have a look at your dive table ... about RNT build up after each dive & the effect of it on our body.

CNS with EANx does happen even when you dive on AIR it happen ... Is Oxygen after all...Is the PO2 limits.

99% of recreational EANx diving are safe & more advantage then diving on AIR as the diving problem is Nitrogen.

My choice of gas has always been EANx.

Where did you hear about the Nasty CNS hit? Please share it.
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