Maximum operating depth

Maximum Operating Depth (MOD) is a term used in scuba diving, particularly in technical diving, to refer to the depth at which a particular breathing gas mixture becomes hazardous due to oxygen toxicity.

Definition

The Maximum Operating Depth of a gas is the depth at which the partial pressure of oxygen (ppO2) in the breathing mix reaches a level considered to be the maximum safe limit. This limit is generally accepted to be 1.4 atmospheres (atm) for normal diving, and 1.6 atm for decompression stops.

Calculation

The MOD is calculated using the formula:

MOD = ((ppO2 / fraction of oxygen) - 1) x 10

Where:

• ppO2 is the maximum safe partial pressure of oxygen, usually set at 1.4 atm for normal diving and 1.6 atm for decompression stops.
• Fraction of oxygen is the proportion of oxygen in the breathing mix, expressed as a decimal.

Considerations

While the MOD provides a guideline for safe diving depths, it is not the only factor to consider. Divers must also take into account nitrogen narcosis, decompression sickness, and the no-decompression limit.

See also

• Equivalent air depth
• Contingency decompression
• Deep diving

References

Maximum operating depth Resources
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