Nitrox maximum depths
The maximum operational depths (MOD) in metres for various Nitrox mixes and oxygen allowances are shown in the table below. Divers are responsible for diving with gases which they have been trained to use.
Quick explanation of PPO2
The partial pressure of oxygen at sea level is 0.21 atmospheres. Oxygen can cause seizures at pressures above 1.4 atmospheres. To keep the partial pressure of oxygen at or below 1.4 atmospheres, it is mixed with proportions of other gases, such as helium, when diving at great depth. Remember the Oxygen will get compressed the deeper you go.
A rough formula is given by:
Depth = ( ( Oxygen Allowance x 10) / Oxygen ratio ) – 10
eg. for Allowance of 1.4 and a Oxygen concentration of 32%
Depth = ( (1.4 x 10) / 0.32) – 10
Depth = (14 / 0.32) – 10
Depth = 43.75 – 10
Depth = 33.75m
FO2 = Fraction of Oxygen in your mixture
PPO2 =Partial Pressure of Oxygen
Nitrox maximum depths table
| FO2 | Maximum depth PPO2 of 1.4 | Maximum depth PPO2 of 1.6 |
|---|---|---|
| 21% | 57 | 66 |
| 22% | 54 | 63 |
| 23% | 51 | 60 |
| 24% | 48 | 57 |
| 25% | 46 | 54 |
| 26% | 44 | 52 |
| 27% | 42 | 49 |
| 28% | 40 | 47 |
| 29% | 38 | 45 |
| 30% | 37 | 43 |
| 31% | 35 | 42 |
| 32% | 34 | 40 |
| 33% | 32 | 38 |
| 34% | 31 | 37 |
| 35% | 30 | 36 |
| 36% | 29 | 34 |
| 37% | 28 | 33 |
| 38% | 27 | 32 |
| 39% | 26 | 31 |
| 40% | 25 | 30 |