95
Formulas
Formulas
Mathematical Formulas
Used in Nitrox Diving Calculations
U.S./Imperial Calculations
Boyle’s Law
P1V1 = P2V2
Dalton’s Law
Or, as formulas:
Pg = Fg x Ptotal
Fg = Pg /Ptotal
Ptotal = Pg /Fg
Converting Depth to Absolute Pressure
Pata D fsw 1
Or
= +
Pata = D fsw + 33
fsw
Converting Absolute Pressure to Depth
Or
Calculating Maximum Operating Depth
In two steps:
P ata = PO2 limit / FO2
followed by:
Or, in one step:
PO
⎛
= −
2limit × ⎟ ⎟⎠
D fsw 1 33 /
Calculating Best Mix
In two steps:
Pata = D fsw +
1
followed by:
FO2 = PO2 limit / P ata
Or, in one step:
PO fsw atm
⎛
FO PO D fsw
⎞
= ⎟ ⎟⎠
⎜ ⎜⎝
= ÷ +
Calculating Equivalent Air Depth
In two steps:
Pata = D fsw +
1
followed by:
Or, in one step:
atm
fsw atm
33 /
fsw atm
33 /
D fsw = (P ata −1atm)×33 fsw/ atm
D fsw = (P ata×33 fsw/ atm)− 33 fsw
D fsw = (P ata −1atm)×33 fsw/ atm
atm fsw atm
FO
2
⎞
⎜ ⎜⎝
atm
fsw atm
33 /
33 /
×
D fsw fsw
fsw atm
33
1
33 /
2 limit
2 2 limit +
atm
fsw atm
33 /
D fsw = (P ata −1atm)×33 fsw/ atm
( ) EAD fsw D fsw fsw FN 33 fsw
⎜ ⎞
⎝
33 2 ⎟ −
0.79
⎠
= ⎛ + ×
Partial
Pressure
Total
Pressure
Gas
Fraction