How is the Minimum Surface Interval (MSI) typically calculated?

The Minimum Surface Interval (MSI) is primarily calculated using dive tables or dive computers. These tools provide essential guidelines regarding the appropriate time a diver should wait at the surface before ascending to a higher altitude or embarking on another dive after a previous one. The calculations take into account factors such as the depth and duration of the previous dive, the residual nitrogen from the dive, and the specific dive profile.

Using dive tables or computers, divers can more accurately determine their MSI to minimize the risk of decompression sickness, which can occur if a diver ascends too quickly without sufficient surface time. This approach also allows divers to follow prescribed safety protocols based on scientific data. While physical fitness and heart rate can contribute to a diver's overall safety and performance, they are not used methodically to calculate MSI as dive tables and computers are. Timing a dive with a stopwatch does not provide the necessary context for decompression regulations, making that approach inadequate for calculating surface intervals.