Ascension is also called the decompression phase. Very simply said it is the time that you need to return to the surface of water after your dive. This phase cannot occur at a random speed, but rather must happen at a specific ascent speed.
Why is ascension necessary?
Since under water the pressure increases continuously, your body has gotten used to the higher pressure during the dive. When you then resurface, your body must adapt conversely to the normal ambient pressure: If the conversion happens too quickly, a barotrauma can be the consequence for instance. In addition, nitrogen can accumulate in the tissue in case of resurfacing too quickly, which can also be dangerous.
In case of greater depths, you must eventually even make several so-called decompression stops during the ascension, in order for your body to slowly get used to the changed pressure.
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