Can You Trust Your Dive Computer?
Dive computers have been used extensively in recreational diving for the last 25 years with a low incidence of decompression sickness (DCS). Statistics show that dive computers generally provide a safer alternative to tables simply because they are (mostly) foolproof. They require no user interface in most cases other than, perhaps, turning them on. Thus, diver error is virtually eliminated.
Dive computers date back to the late 1950s, but early designs were not always reliable. Electronic technology has improved these designs to the point that any serious diver would be foolish to dive without one. It could therefore be argued that their use was “successful” in many respects. However there have been reported cases of DCS, after recreational divers followed their dive computer on no-decompression dives. Recent DAN Europe data suggests that around 80% of neurological DCS cases did not violate their diving computer recommendation.
Recreational dives are dives limited in depth and time such that the diver may ascend to the surface at any time with an acceptably low probability of suffering decompression sickness (DCS). Diving beyond these limits requires the diver to stop on his way to the surface to decompress. Hence, they are known as “no-stop” limits.
Decompression theory, no-stop limits and decompression stops have come a long way since physiologist J.S. Haldane, drafted a set of diving depth/time tables to suit a human circulatory system.
Over the years research into the factors leading to DCS has continued and is still not an exact science due in part to the large number of variables present in a diver and the circumstances of every dive. Diver fitness, hydration and exercise level before and after diving all appear to have an effect on the likelihood of developing DCS.
Are we then to abandon our dive computers? Of course not! They still offer the best estimation of limits for multiple multi-level recreational dives. But treating dive computer information as the absolute truth and pushing no-stop times to their limits is to raise risk. Be conservative and give yourself a safety margin (in the same way as you would make a 5 metre safety stop - not essential but a really good practice). In that way you can be assured you have taken the most appropriate steps towards a safe and fulfilling dive.