Nitrox safer than air

[Scuba]

Thank you all for your replies.

One more question.

Given that the advantages provided by Nitrox in terms of increased bottom time and/or DCS safety margin is wheighed against the increased risk of oxygen toxicity. How much is one increasing the risk of oxygen toxicity when using Nitrox, compared to air, when all tables and safety precautions are taken?

Peter

 

[WreckWriter]

Scuba once bubbled...
Thank you all for your replies.

One more question.

Given that the advantages provided by Nitrox in terms of increased bottom time and/or DCS safety margin is wheighed against the increased risk of oxygen toxicity. How much is one increasing the risk of oxygen toxicity when using Nitrox, compared to air, when all tables and safety precautions are taken?

Peter

Not at all PROVIDING you keep your PO2 at 1.4 or less, same as you should with any gas. If you dive air to a 1.6 PO2 (218 FSW) and dive EANx32 to a 1.6 PO2 (132 FSW), you have the same risk of toxxing out.

Tom

 

[Uncle Pug]

Is all we dive to 100fsw. No air. No *best mix*. Just EAN32 and we figure our dives with air tables but know that we have a 20% safety factor and can adjust if need be. We do a 1 hour SI and figure our second dive with air tables. Simple.

 

[Stone]

Uncle Pug once bubbled...
. . .we figure our dives with air tables but know that we have a 20% safety factor . . .

UP,

How do you "know" your safety factor is 20%? Is it calculated or rule of thumb?

 

[Uncle Pug]

Stone once bubbled...
How do you "know" your safety factor is 20%? Is it calculated or rule of thumb?

What is the EAD of EAN32 on a 100' dive?

 

[O-ring]

What is the EAD of EAN32 on a 100' dive?

Let's see...according to DSAT tables it is 81 feet. Roughly 20%...

 

[Uncle Pug]

O-ring once bubbled...
Let's see...according to DSAT tables it is 81 feet. Roughly 20%...

Would that 20% be consistent over the whole range of depths or does it vary?

 

[Northeastwrecks]

Dear UP:

I've always wondered about why we dive Nitrox 32 at anything less than 100 fsw.

Certainly it makes some sense when you're down around 70 - 80 feet. Nice increase in bottom time and no real problem with PO2.

That said, why not dive Nitrox 50 (or some such mix) when your on a 35 foot bug hunt or a shallow wreck? You feel great coming out and you have no risk of acute ox tox because you're still well under 1.4.

The only reason I can come up with is the increased risk of chronic O2 tox. But that won't happen if I watch my DSAT table.

I'm not taking my DIR-F course until this October, when I'm told that I will learn such things.

 

[O-ring]

EANx32

Depth      DSAT EAD             %
20            13                35 
30            21                30
40            30                25 
50            38                24
60            47                22
70            56                20
80            64                20
90            73                19
100           81                19
110           90                18

Average safety margin = 23%

Looks about right...

 

[Uncle Pug]

... but why bother.... you can stay down almost forever on a 35 fsw bug hunt anyway! Well longer than any gas supply you can take with you will last.

We use the standard 32% mix and don't have to futz around getting a higher O2 content... EAN32 is cheap and easy to make (& bank)... it takes me a little more time and effort to get the 50% for our deco bottles.

But the bigger issue might be.... since there is no chance of anything other than EAN32 going into my single LP104s there is no chance of me accidentally taking a jug of 50% down on a dive to 100'.

Keep it simple... keep it clean... keep it safe.

Maybe after taking the GUE Tech 1 you will start using 30/30 for those dives that are 80~120.