What is the maximum operating depth (MOD) meant to limit exposure to?

The maximum operating depth (MOD) is defined to ensure that divers do not exceed a partial pressure of oxygen (ppO2) of 1.4 bar or less during their dives. This is crucial because higher levels of ppO2 can lead to oxygen toxicity, which poses serious risks to divers, including convulsions and impaired cognitive function, particularly when diving at depths where the ambient pressure increases.

By limiting the ppO2 to 1.4 bar, divers can safely utilize enriched air nitrox blends, allowing for longer bottom times and shorter surface intervals while minimizing the risk of oxygen toxicity. This established limit is a standard in dive training and practice for safe diving protocols.

The other options provided represent either incorrect values for ppO2 or misunderstand the concept of MOD in relation to nitrogen limits, non-decompression limits, or fraction of oxygen in the breathing gas, which are not intended to set the MOD criterion effectively based on safety for oxygen exposure.