Nitrox Mix

[DuboisP]

Moose explained it perfectly, and I could have answered my own question if it had not been so long since dealing with it. I WILL be re-opening the book and tables on it tonight though. And you from the Charlotte area?

After talking with my brother, and not really knowing how deep (which I thought he knew) or how long we are going to be down, but will work all that out before jumping in. Decided to drop back to EAN 32. Would rather play it safe with this mix rather than possible ending up with CNS.

don't worry with CNS for your recreational dives.

Bryan St.Germain is true
you must dive more than 300 min to have 100%, and you will be out of gas before.

rebreather divers or cave divers have often more than 100%

 

[Krenath]

sure, if you're using ATA

but the question was
(46.2/0.40)-33

what is this 46.2 ?

Not the way I'd do it, but it appears that the 46.2 is 33ft * 1.4 as if Lead_carrier multiplied by 33 earlier than I would have. I don't see the point of doing it that way, as it seems to be more effort since you're multiplying by (whatever 1 ATA of depth in your chosen measuring system is) twice.

The MOD formula is this. MOD = { (Max PPO2 * 33) / FO2 } - 33

can be restated slightly more concisely as:

MOD = (( MaxPPO2 /F02 ) -1 ) * (10M or 33ft)

But the formulae are functionally equivalent.

The 46.2 by itself doesn't mean anything directly useful. It's just an intermediary step in the formula. You might as well ask what the 3.5 means when you divide (1.4 / 0.40 ). 3.5 of what?

EDIT: (well, in this case, the 3.5 the total pressure (water column + air above it) in atmospheres that brings a 40% O2 mix to 1.4%PPO2 but that's beside the point.)

 

[DuboisP]

You might as well ask what the 3.5 means when you divide (1.4 / 0.40 ). 3.5 of what?

3.5 bar/ata of absolute pressure, so 25m
I correct
(1.4 ata * 40 %) - 1 ata) * 10 m = 25 m

 

[Chugwhump]

Attacking the metric system?
You have got to be kidding me.
Base 10 simplifies (U.S. Currency for a really long time now).
Base 12 simplifies
Base whatever...simplifies.

I use the following units of measure for length......
Arpents, International Foot, US Survey Foot, Vara (several of them), Furlongs, Meters, Fathoms, whatevers, and the list goes on and on and on.
I use them all.
It's lotsa' fun...when you learn how.

Chug
Land Surveyor
My apologies to all concerned for

 

[Krenath]

3.5 bar/ata of absolute pressure, so 25m
I correct
(1.4 ata * 40 %) - 1 ata) * 10 m = 25 m

1.4 / .4 = 3.5 This is TOTAL ATA of pressure. 1 ATA of that TOTAL is above water and the other 2.5 ATA is below the water

We subtract 1 ATA because the underwater portion is what we care about. And once you subtract out the 1 ATA above the surface and multiply the remainder by 10m or 33ft, you get the maximum operating depth with a 40% O2 mix.

Edit : Sorry, I though you were saying you were correcting me as opposed to saying you were correcting the formula

 

[Krenath]

Attacking the metric system?
You have got to be kidding me.
Base 10 simplifies (U.S. Currency for a really long time now).
Base 12 simplifies
Base whatever...simplifies.

I use the following units of measure for length......
Arpents, International Foot, US Survey Foot, Vara (several of them), Furlongs, Meters, Fathoms, whatevers, and the list goes on and on and on.
I use them all.
It's lotsa' fun...when you learn how.

Chug
Land Surveyor
My apologies to all concerned for

Yup:
In fathoms: (1.4 ata * 40 %) - 1 ata * 5.5 fathoms = 13.75 fathoms MOD
In furlongs: (1.4 ata * 40% ) - 1 ata * 0.05 furlongs = .125 furlongs MOD
In leagues: (1.4 ata * 40% ) - 1 ata * 0.00179985601 leagues = 0.00449964003 leagues

In base 7 & meters:
(1.2547 ata / .2547) - 1 ata * 137 meters = 347 meters MOD

(For those not following along, in base 7, "34" means "3 sevens plus 4" rather than "3 tens plus 4")

No matter what numeric base or measuring system you use, it's just a matter of conversion factors.

The formula itself does not ever change. Only the conversion factors

 

[Jax]

don't worry with CNS for your recreational dives.

Bryan St.Germain is true
you must dive more than 300 min to have 100%, and you will be out of gas before.

rebreather divers or cave divers have often more than 100%

Am I the only one thoroughly disturbed that someone would even state the thought, "Don't worry about . . . "

WTH?

 

[Kevin Carlisle]

Am I the only one thoroughly disturbed that someone would even state the thought, "Don't worry about . . . "

WTH?

Nope. In theory he is correct but everyone does handle the gas different. I know a friend who has to keep her P02 around 1.2 because she is sensitive to 02.

 

[DuboisP]

Nope. In theory he is correct but everyone does handle the gas different. I know a friend who has to keep her P02 around 1.2 because she is sensitive to 02.

the sensitivity to O2 concerns 2 notions :
neurological (CNS)
pulmonary (OTU)

i assume she is sensitive on the pulmonary notion ?

 

[Kevin Carlisle]

the sensitivity to O2 concerns 2 notions :
neurological (CNS)
pulmonary (OTU)

i assume she is sensitive on the pulmonary notion ?

I'm sure you are aware 02 is narcotic too, she gets very narcosis very easy on nitrox mixes. She tolerates the nitrogen better than a rich 02 mix. So her deco obligations are usually more than ours.