When should divers be switched to oxygen during decompression stops?

Switching divers to oxygen during decompression stops is crucial for minimizing the risk of decompression sickness and optimizing inert gas elimination. The correct answer indicates that divers should switch to oxygen upon arrival at an oxygen stop, which is strategically designed to allow for the efficient off-gassing of nitrogen accumulated during the dive.

Using oxygen at these designated stops helps to enhance the effectiveness of the decompression process. By breathing pure oxygen, divers can reduce the partial pressure of nitrogen in their tissues more quickly, thereby accelerating the elimination of nitrogen from their bodies. This practice is particularly important at certain depths where the water pressure is significant, and nitrogen is more readily absorbed into the body.

Choosing to switch to oxygen only when reaching the surface does not utilize the physiological advantages offered by oxygen during the critical decompression phase. Initiating oxygen use at the start of ascent may not be ideal either, as the divers would benefit more from regular air at deeper depths where the nitrogen loading is most significant. Utilizing oxygen only at the end of a dive fails to provide the necessary support during the time when divers are most at risk for decompression-related issues. Thus, the timing of oxygen supplementation is key, making the arrival at designated oxygen stops the optimal moment for this transition.