MODMaximum Operating Depth
Maximum Operating Depth of a breathing gas with specific oxygen fraction limited by maximum oxygen partial pressure.
MOD is the deepest point where a gas can be breathed before its oxygen partial pressure rises above your limit. Go deeper and the risk of CNS oxygen toxicity grows quickly.
How it works
MOD = (ppO₂ max ÷ FO₂ − 1) × 10 m
- ppO₂ max your oxygen limit: 0.7 to 1.6 bar, typically 1.4 on the bottom and 1.6 for deco
- Rounding rounded down to the whole metre, so you never exceed the limit
Example
- Gas
- Air (21 % O₂)
- ppO₂ max
- 1.4 bar
- MOD
- (1.4 ÷ 0.21 − 1) × 10 = 56.7 → 56 m
How it works
MOD = (ppO₂ max ÷ FO₂ − 1) × 32.8 ft
- ppO₂ max your oxygen limit: 0.7 to 1.6 bar, typically 1.4 on the bottom and 1.6 for deco
- Rounding shown to the nearest foot
Example
- Gas
- Air (21 % O₂)
- ppO₂ max
- 1.4 bar
- MOD
- (1.4 ÷ 0.21 − 1) × 32.8 ≈ 186 ft
Take it to the dive site
The same calculator works offline in the Deep Tools app, together with the dive planner, dive log and blender.
