Which aspect must be assessed in a diving plan at altitude?

When planning a dive at altitude, assessing the need for altitude correction measures is crucial due to the changes in atmospheric pressure that occur at higher elevations. At altitude, the barometric pressure is lower than at sea level, which can significantly affect the way nitrox and air dissolve in the body, altering the risk of decompression sickness and the effectiveness of dive tables. Therefore, divers must adjust their dive profiles and limits accordingly to compensate for these effects. This may involve using specific dive tables for altitude diving, ensuring adequate safety stops, or even utilizing different gas mixtures to mitigate the risks associated with decreased pressures.

While the gear required, maximum allowable depth, and diving operation conditions are all important elements of a dive plan, they do not address the unique physiological changes that occur when diving at altitude. These factors can typically be evaluated separately from altitude considerations, but altitude correction directly pertains to the safety and health of the diver during their underwater activities.