What does decompression mean in diving?

Answer 1

There are 2 possible answers. One is a simple answer to what is decompression in diving. The answer to that is simply ascending back to the surface. Any time pressure is reduced (i.e swimming shallower), the diver is decompressing. So many divers will say that all dives are decompression dives since that is an accurate description. The other possible answer is what is decompression sickness or illness. This occurs when a diver has not adequately decompressed back to the surface. In recreational diving, actual decompression stops are not required even though a "safety" stop or stops are always recommended. The purpose of the stops is to allow some of the inert gas absorbed during the dive from breathing (which is nitrogen for air or oxygen enriched air mixtures) to be released from the body prior to surfacing so the extra nitrogen does not result in "too many" bubbles. Bubbles can occur since air is comprised of roughly 79% nitrogen and 21% oxygen. Nitrogen is an inert gas since it does nothing other than just sitting there (as compared to oxygen that is metabolized and used) ... so nitrogen can build up during a dive due to the pressure on the body from being underwater. Bubbles result in tissues after almost every dive, but the body can handle them nicely, so it is excessive or too many bubbles that become a problem. The same answer applies to dives that are planned decompression stop dives that technical or commercial divers do. These dives will require stops at multiple depths to reach the surface again often using multiple different decompression gases during the different stops to accelerate the decompression times. The longer the dive, the longer the required decompression due to greater absorption of inert gas. But if adequate decompression is not done, then bubbles will form in body tissues which will result in decompression sickness commonly known as the bends ... which requires treatment in a recompression chamber ... to recompress the diver and make the bubbles smaller so they can be reabsorbed by the diver during the treatment. See the links below for some other articles on decompression and diving.