Why you must never hold your breath in cylinder diving and the serious dangers that result from that.
One of the most important rules of cylinder diving: never hold your breath.
Air in the lungs expands during ascent. If you hold your breath while rising, the air expands faster than the lungs can handle, and this may cause a lung rupture.
When air is cut off. The correct solution is a continuous exhale during ascent, not holding the breath.
Always remember: exhale during ascent. This rule has no exception.