SAFETY To Stop or Not To Stop – That is the Question – by Dan Orr, President, Dan Orr Consulting
First of all, it is important to under- stand that all dives involve decompres- sion, even those we call "no-decompression" dives. As every diver knows, our body tissues absorb and eliminate gases (nitrogen, for exam-
calculate safe dive limits by factoring in various real-time measurements, but the safety and effectiveness of these al- gorithms can vary. Divers should understand these limita- tions and consider their personal risk factors when diving. Safety stops also help divers control their rate of ascent to the surface during the critically important final stages of their ascent. Safety stops do help ensure a safe and controlled re- turn to the surface. An added benefit of the safety stop is to help enhance our situational awareness. The pause at the safety stop depth pro- vides an opportunity to survey surface conditions, look for boat traffic, and check that all equipment is secure before surfacing.
ple) during the descent and ascent of every dive. In years past, the decompression from a non-decompression dive was satisfied by a slow, controlled ascent to the surface. A controlled ascent from every dive is crucial to assure proper elimination of absorbed gases in order to reduce the likeli- hood of decompression sickness (DCS). This brings up the importance of the safety stop in recreational scuba diving. Scuba diving safety stops are, as we know, brief pauses dur-
Safety stops are generally per- formed at a depth of 15-20 feet (5-6 meters) for 3-5 minutes. The safety stop time can also be extended if a diver has come close to the no-decompression
ing the ascent from a scuba dive, primarily intended to reduce the risk of DCS. While not manda- tory, they are strongly recom- mended for every dive and have become a standard part of safe dive planning.
limits, has had an increased workload during the dive which could increase the absorption of additional gas, or where something has occurred during the dive that possibly in- creased susceptibility to DCS. Be sure that the possibility of a change in the dive plan is something you have previously discussed with your diving companion(s) and divemaster. If a change is going to be made, clearly communicate your in- tentions to your diving companion(s) before proceeding, and make sure that you have sufficient breathing gas to safely ex- tend the time at your safety stop. It's important that we understand the difference between safety stops and mandatory decompression stops. Safety stops are, as we have stated, considered standard practice for recreational scuba dives within no-decompression limits, providing an opportunity to allow additional time for the tis- sues to eliminate accumulated nitrogen in the tissues, reduc- ing the likelihood of DCS. A scuba diving safety stop, while not mandatory, is a highly recommended precautionary measure to enhance safety during ascent. However, there are situations where a safety stop might be modified or even skipped, primarily in emergencies or when other potential risks far outweigh the benefit of the stop. Decompression stops, on the other hand, are MANDA- TORY and required when a diver has exceeded the no-de- PAGE SEVEN | SCUBA DIVING INDUSTRY
The idea of safety stops in scuba diving is attributed to ini- tial research into ascent rates and bubble formation by re- searchers, including some early groundwork by Dr. Andrew Pilmanis in 1974. They were first mentioned in recreational diving as early as 1984 in the PADI Open Water Diver Man- ual. In 1994, graduate student Donna Uguccioni wrote her master’s degree thesis on safety stops that expanded on Dr. Pilmanis' work. Donna’s study used Doppler ultrasound scans, demonstrating that divers who practiced safety stops had fewer intravascular bubbles in their bloodstream follow- ing dives than those who did not make a safety stop. Safety stops in recreational scuba diving are important for a number of reasons. Primarily, they help reduce the likeli- hood of DCS by allowing additional time for the body’s tis- sues to off-gas nitrogen during the ascent, potentially providing some enhanced safety margin. The dive computers that are so common in diving today calculate no-decompres- sion limits, but they cannot guarantee immunity from DCS. Safety stops add that extra layer of conservatism so impor- tant in mitigating the risk of DCS. It is important to under- stand that dive computer algorithms, while designed to reduce the likelihood of DCS, are based on theoretical mod- els and, therefore, do have limitations. They are designed to
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