origin of the constant values in the EAD and PO2 formula calculations ?

[Mario]

Hello,

Can some one explain me or tell me a web link in which is explained
the origin or source of the formulas for calculating:

EAD= (((1-O2%) x (Depth+10) )/ 0.79)-10

0.79 comes from where?

PO2=(((Depth+10))/10)x 02%

this formula comes from where?

I would like to understand where these formulas come from.

Thanks,

Mario

[Keith Lawrence]

Post by Mario
Can some one explain me or tell me a web link in which is explained
EAD= (((1-O2%) x (Depth+10) )/ 0.79)-10
0.79 comes from where?
PO2=(((Depth+10))/10)x 02%
this formula comes from where?
I would like to understand where these formulas come from.

Your basic diving course and the Nitrox course should explain it.

The 0.79 comes from the N content of ordinary air, around 21% O2, 79% N

The Depth + 10 =MUST= be in metres, the +10 (then / 10) gives you the
additional 1 BAR pressure of the atmosphere to give you the absolute
pressure at depth. e.g. 10m of water gives you (10 + 10) / 10 = 2 BAR
absolute.

HTH, do the course

Keith L

[TonyH]

I blame the instructors.

They either can't teach properly, or if they have a student who simply can't
do the maths, then they haven't got the balls to be honest and fail
someone!

Post by Keith Lawrence

Post by Mario
Can some one explain me or tell me a web link in which is explained
EAD= (((1-O2%) x (Depth+10) )/ 0.79)-10
0.79 comes from where?
PO2=(((Depth+10))/10)x 02%
this formula comes from where?
I would like to understand where these formulas come from.

Your basic diving course and the Nitrox course should explain it.
The 0.79 comes from the N content of ordinary air, around 21% O2, 79% N
The Depth + 10 =MUST= be in metres, the +10 (then / 10) gives you the
additional 1 BAR pressure of the atmosphere to give you the absolute
pressure at depth. e.g. 10m of water gives you (10 + 10) / 10 = 2 BAR
absolute.
HTH, do the course
Keith L

[Lee Bell]

Post by Mario
Hello,
Can some one explain me or tell me a web link in which is explained
EAD= (((1-O2%) x (Depth+10) )/ 0.79)-10

That's the formula in meters. Most here are more likely to do the formula
in feet.

Post by Mario
0.79 comes from where?

That's the partial pressure of nitrogen at 1 atmosphere

Post by Mario
PO2=(((Depth+10))/10)x 02%
this formula comes from where?

The partial pressure of O2, and other gasses as well, varies with depth.
The sum of all partial pressures will always equal the the total pressure.
In the formulas you've shown, the gas is presumed to consist only of
nitrogen and oxygen at .79 and .21 percent respectively for air. At 10
meters, approximately 2 atmospheres, you're talking partial pressures of
1.58 and .42 which, you'll note, add to 2 atmospheres.

Lee

[Pete Melbourne]

Post by Mario
Hello,
Can some one explain me or tell me a web link in which is explained
EAD= (((1-O2%) x (Depth+10) )/ 0.79)-10
0.79 comes from where?
PO2=(((Depth+10))/10)x 02%
this formula comes from where?
I would like to understand where these formulas come from.

It is all Dalton's Law which you should have been taught in your basic
scuba and Nitrox courses
--
Pete

news 'at' melbourne 'dot' me 'dot' uk

[TonyH]

Post by Pete Melbourne

Post by Mario
Hello,
Can some one explain me or tell me a web link in which is explained
EAD= (((1-O2%) x (Depth+10) )/ 0.79)-10
0.79 comes from where?
PO2=(((Depth+10))/10)x 02%
this formula comes from where?
I would like to understand where these formulas come from.

It is all Dalton's Law which you should have been taught in your basic
scuba and Nitrox courses

I didn't know that peanuts were involved! Where'se Percy?

--

Post by Pete Melbourne
Pete
news 'at' melbourne 'dot' me 'dot' uk

[e***@bellsouth.net]

0.79 is the partial pressure of nitrogen at sea level. You use this formula
to calculate your equivalent air depth or your equivalent narcotic depth
depending on what type of diving your doing. You use the EAD to determine
what air depth your diving when your diving a nirtox mixture. However the
formula is more correctly written
EAD= [FN2 / .79 x (depth mswa)] - 10 msw

your PO2 formula is used to determine your oxygen partial pressure at a
given depth. This is very important to know since exposure to high practical
pressure of oxygen can kill you in a hurry. On the flip side of that
prolonged exposure to lower oxygen partial pressure > .55ata and < 1ata can
also cause some rather unpleasant side effects. The long and the short of
this is it is very important to track your oxygen exposure and if you have
not been trained in the proper use of breathing gases other than air you
shouldn't use them or you will probably kill your self

Post by Mario
Hello,
Can some one explain me or tell me a web link in which is explained
EAD= (((1-O2%) x (Depth+10) )/ 0.79)-10
0.79 comes from where?
PO2=(((Depth+10))/10)x 02%
this formula comes from where?
I would like to understand where these formulas come from.
Thanks,
Mario

[Rich Lockyer]

Post by Mario
Hello,
Can some one explain me or tell me a web link in which is explained
EAD= (((1-O2%) x (Depth+10) )/ 0.79)-10
0.79 comes from where?

Percentage of nitrogen in the atmosphere. You are converting to an
equivalent AIR number, so you need to factor for the composition of
AIR.

Post by Mario
PO2=(((Depth+10))/10)x 02%
this formula comes from where?

Let's say EAN50 at 30m, plus 10 would be 40. 40/10=4.0 4.0*0.50=2

In the metric system, depth=bar*10, so 30m would equal 3bar. You need
to add one to get to 4bar because of the 1ata surface pressure. You
are adding 10 instead of 1 because you are using the simplistic
formula of working directly with depth.

The formula would be just as accurate if changed to
"PO2=(Depth/10+1)x 02%" where you convert depth to pressure. That's
how we do it in the Imperial system... 100ft/33=3.03+1=4.03*0.50=2.06

Close enough.

Post by Mario
I would like to understand where these formulas come from.

Take a class.

You've been on this forum for over a year asking the most very basic
questions. You've claimed to have been certified many years ago, yet
you continue to ask questions that indicate a complete lack of
understanding of the most basic concepts.



--- Rich
http://richlockyer.tripod.com/