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Review of Physics. Physics - Introduction. Pressure T Calculate ppO 2 at any given depth MOD Required EAN% Equivalent Air Depth Calculations. ppg. Fg. P. Pressure T. ppg = Fg x P Fg = ppg /P P = ppg / Fg ppg – Partial Pressure of a gas Fg – Fraction of gas
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Physics - Introduction • Pressure T • Calculate • ppO2 at any given depth • MOD • Required EAN% • Equivalent Air Depth • Calculations
ppg Fg P Pressure T ppg = Fg x P Fg = ppg/P P = ppg/Fg ppg – Partial Pressure of a gas Fg – Fraction of gas P - Absolute Pressure
Pressure T Calculations What is the ppO2 of EAN 34 at 28 metres? ppO2 = FO2 x P = 0.34 x 3.8 = 1.292 bar Can calculate ppO2 at any given depth
Pressure T Calculations What is the ppN2 of EAN 34 at 28 metres? ppg = Fg x P FN2 = 1 – 0.34 = 0.66 P = 3.8 Bar ppN2 = 0.66 x 3.8 Bar = 2.508 Bar
Pressure T Calculations At what depth does EAN 50 have a ppO2 of 1.6 bar? P = ppg/Fg = 1.6/0.5 = 3.2 Bar = 22 metres Allows Calculation of Depth Limit for a given EAN mix
Pressure T Calculations What Nitrox mix will we use to give a ppO2 of 1.6 at 10m? ppO2 = 1.6 bar P = 2 Bar FO2 = ? FO2 = ppO2/P = 1.6/2 = 0.8 Answer: EAN 80 Allows Calculation of EAN mix to use
Equivalent Air Depth (EAD) • ppN2 of Nitrox = ppN2 of Air at shallower depth • Air Tables • Calculate EAD using Pressure T
Equivalent Air Depth (EAD) What is the EAD of EAN 35 at 30 metres? P = 4 Bar FN2 = 1 – 0.35 = 0.65 ppN2 = ? ppN2 = P x FN2 = 4 x 0.65 = 2.6 bar At what depth is ppN2 of Air = 2.6 bar?
Equivalent Air Depth (EAD) ppN2 = 2.6 bar FN2 = 0.79 P = ? P = ppN2/FN2 = 2.6/0.79 = 3.29 Bar = 22.9 metres (23 metres) For EAN 35 at 30m, can use Air Tables at 23m
Physics Summary • Pressure T • Calculate • ppO2 at any given depth • MOD • Required EAN% • Equivalent Air Depth • Calculations