Scuba decompression refers to the process of allowing dissolved gases, primarily nitrogen, to slowly off-gas from a diver’s body during the ascent to the surface after a dive. When a diver descends underwater, the pressure of the water increases and more nitrogen is dissolved into the diver’s body. If the diver ascends too quickly, this dissolved nitrogen can come out of solution and form bubbles in the bloodstream, which can lead to a condition known as decompression sickness (DCS) or “the bends”.
To prevent DCS, divers use a dive computer or dive tables to plan their dives and calculate the appropriate amount of time to spend at different depths. This time is known as “bottom time” and it includes the time spent at the maximum depth and a safety margin for the ascent. The computer or tables also take into account the diver’s breathing gas, which can affect the rate at which nitrogen is dissolved into the body.
During the ascent, the diver will stop at specific depths for a certain amount of time, known as “decompression stops”, to allow the nitrogen to off-gas from the body. These stops are usually between 3 and 6 meters (10 and 20 feet) and are longer the deeper the diver has been.
The diver will then continue the ascent, making additional stops as necessary, until reaching the surface. The diver should continue to monitor their dive computer or tables throughout the ascent to ensure they are following the correct profile and making the appropriate stops.