Why should divers avoid flying immediately after diving?

Divers should avoid flying immediately after diving primarily to prevent an increased risk of decompression sickness due to rapid pressure change. When a diver ascends to the surface, they must adhere to safe ascent rates and may need to perform safety stops to allow excess nitrogen absorbed in the body to safely leave the body. If a diver flies right after diving, the rapid decrease in atmospheric pressure during ascent in a plane can lead to nitrogen bubbles forming in the tissues or bloodstream, which may result in decompression sickness (DCS). This happens because the reduced pressure allows the nitrogen, which is dissolved in the body under higher pressures while diving, to come out of solution and form bubbles.

This risk is particularly significant if the diver hasn't allowed enough time for the nitrogen to be off-gassed after diving activities. Typically, it is recommended that divers wait a minimum of 24 hours after a multi-day dive excursion or deeper dives before flying. This time allows the body to eliminate nitrogen safely, thus minimizing the risk of DCS.