Why Do Divers Have to Wait to Fly?
Flying after diving
The answer relates to pressure inside the body. If the surface is the baseline, each person has one atmosphere of weight at this level. Divers do not notice this weight. However, for every 33 feet (10 meters) of sea water (fsw = feet of seawater) that a diver descends on a dive, another atmosphere of weight is added to the pressure. This pressure turns nitrogen in the blood into solution, and the plasma becomes supersaturated. During ascension, the opposite is true. Pressure decreases as dives ascend altitude. The decrease in pressure causes nitrogen to come out of solution and form bubbles in the blood stream.
Bubbles form when divers
- ascend to the surface after a dive
- ascend to altitude after a dive (as in flying)
- ascend to a higher surface altitude without pressure
During the required wait time, divers’ bodies blow off saturated nitrogen bubbles and reduce pressure before flying. It is the same reason divers use surface intervals between dives. It is also the reason divers make safety stops on the way up to the water’s surface after each dive.
Recommendations for Flying After Diving
The Professional Association of Diving Instructors (PADI) and Divers Alert Network (DAN) recommend the following wait times for flying after diving:
- A minimum pre-flight surface interval for a single dive is 12 hours.
- A minimum pre-flight surface interval for repetitive dives or multiple days diving is 18 hours.
Following these recommendations greatly reduces the risk of decompression sickness (DCS). The recommendations do not guarantee 100% that a diver will avoid DCS, which is also known as the diver’s disease called the bends. Another important factor to consider is dehydration. Divers should stay well hydrated when on a dive trip.
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Diving After Flying
Diving after flying is not a problem. Divers can head straight to the ocean for a dive upon arrival at the airport without the risk of DCS. High concentration of nitrogen in the blood occurs only after diving. The nitrogen typically becomes supersaturated and forms bubbles at lower pressures. Before the first dive, a normal amount of nitrogen is in the blood.
Note that longer flights allow more time for dehydration, which is also a problem in DCS. Scuba divers should drink plenty of non-alcoholic fluids on a long flight to prevent dehydration. Some divers tend to arrive in a hot country and head straight to the bar. However, alcohol contributes to dehydration, so drink extra water.