What is the minimum time that must be considered as 'dead time' when a diver has to shift back to air?

The minimum time that must be considered as 'dead time' when a diver has to shift back to air is commonly cited as 5 minutes. This period is crucial because it allows for the dissipation of inert gases, primarily nitrogen, absorbed during the dive. During this time, the diver should remain at a shallow depth to reduce the risk of decompression sickness upon returning to air.

This 'dead time' is based on physiological data regarding how quickly nitrogen is eliminated from the body after exposure to increased pressures during diving. By adhering to this guideline, divers are able to safely manage their ascent and avoid adverse health effects associated with rapid changes in pressure, such as the bends.

Considering the other options, 2 minutes would be insufficient time for gas elimination, while both 10 and 15 minutes extend beyond the necessary minimum and could add unnecessary delay to the dive operation. Thus, the 5-minute dead time is supported by training protocols and safety standards in the diving industry.