The most popular diving spots can often only be reached by plane. Thereby, a plane often reaches a flying altitude of ca. 5,000 metres even for short-haul flights. For long-distance flights this can be significantly higher. Since the air pressure at such heights falls greatly, the question arises as to whether a flight directly influences your decompression time before or after your dive?
First of all the good news. Even at a flying altitude of 5,000 metres you are not exposed to the low external pressure of course. Or else, the fast ascent of the plane would not be possible at all. Because the crew and the passengers would suffer from decompression sickness before the plane reaches the necessary altitude. This is why there is an artificially created balanced pressure inside the cabin. Thus passengers can travel without any danger.
For divers it is important to know: The pressure in the cabin of a plane is much lower than in normal environments though. You must reckon with an ambient pressure of about 0.75 bar on the plane. This corresponds to the natural ambient pressure at an altitude of 2,500 metres. This is the reason why the decompression time definitely changes if you go diving directly after flying.
Since the difference between the ambient pressure of where you took off from and the pressure under water is higher than normal, the risk of decompression sickness is higher. The same is true if you get on a plane directly after ascending.
Recommendations when flying and diving
Because you are exposed to a lower ambient pressure on the plane, you should not fly 12 to 24 hoursbefore and after a dive. In this time your body has eliminated the surplus of oxygen and is back to a normal ambient pressure of ca. 1 bar.
By the way, the same is also valid for travelling to a high mountain region, because here the ambient pressure is reduced as well.
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