What does the required surface interval depend on before ascending after diving?

The required surface interval before ascending after diving is influenced significantly by the planned increase in altitude. This is primarily because ascending to higher altitudes can increase the risk of decompression sickness or "the bends," which occurs when nitrogen dissolved in the bloodstream forms bubbles as pressure decreases.

When divers plan to ascend to a higher altitude after diving, it's essential to allow enough time for the body to safely eliminate excess nitrogen acquired during the dive. The surface interval is a crucial period where divers can off-gas nitrogen, ensuring they are not at risk of forming bubbles when exposed to lower atmospheric pressure at higher altitudes.

While the previous dive's depth, the number of surface intervals completed, and the type of gas used during the dive are factors to consider in overall dive planning and safety, they do not specifically dictate the necessary surface interval changes related to altitude ascent like the planned increase in altitude does. Understanding this relationship is key for maintaining safety and minimizing risks in diving operations.