Maximum Operating Depth (MOD) — What It Is and Why It Matters
Maximum operating depth (MOD) is the deepest depth at which a specific breathing gas can be safely used, based on the maximum allowable partial pressure of oxygen (typically 1.4 bar for the working phase of a dive). Going beyond the MOD puts the diver at risk of central nervous system oxygen toxicity, which can cause seizures underwater.
MOD is calculated using the formula: MOD = ((ppO2 max / FO2) − 1) × 10 meters. For EAN32 at 1.4 ppO2: MOD = ((1.4 / 0.32) − 1) × 10 = 33.75 meters. Every nitrox-capable dive computer can calculate and display MOD when you input your gas mix.
Frequently Asked Questions
What is the MOD for EAN32?
At a ppO2 limit of 1.4 bar, the MOD for EAN32 is approximately 33 meters (110 feet). At 1.6 ppO2 (decompression limit), the MOD extends to about 40 meters (130 feet). Always use the more conservative 1.4 limit for the active portion of your dive.
Does my dive computer warn me if I exceed MOD?
Yes. Any nitrox-capable dive computer will display warnings — both audible and visual — if you descend beyond the MOD for your set gas mix. Some will flash the depth display, change screen color, or display a dedicated MOD violation warning.
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