Decompression Diving — A Technical Aspect of Diving Deeper, Longer

A longtime leader in the US Navy SEAL, Lieutenant Adam Schwarze commands missions and has also been responsible for innovations in SEAL Delivery Vehicle (SDV) equipment. Adam Schwarze is an experienced diver with first-hand knowledge of technical aspects such as decompression diving.

Decompression diving involves extending beyond No Decompression Limits (NDLs) as a way of extending one’s available time in the water at a specific depth. The physiology behind this is that nitrogen inhaled while descending dissolves into the bloodstream and various body tissues in a process known as “on-gassing.” As one ascends again, off-gassing occurs. The nitrogen diffuses from the tissues back to the blood and is perfused into the lungs, finally expelled as breath.

On- and off-gas rates vary significantly depending on depth and length of time diving at depth. Other variables include body type, fitness level, and how quickly you ascend and descend. In recreational diving, NDLs are set through the use of dive computers to ensure one doesn’t take on more nitrogen than can be off-gassed for a direct ascent to the water’s surface.

With decompression diving, one is taking on nitrogen that exceeds NDLs, and thus a series of timed stops need to be made on the ascent to give the gas time to exit the tissues back into the lungs. Failing to do this runs the risk of decompression sickness or the bends. The rewards of decompression diving are lengthier bottom time and more opportunities to explore features, whether an underwater canyon or a shipwreck.