What is the main concern when ascending too quickly?

The primary concern when ascending too quickly is the risk of decompression sickness and lung expansion injuries. When a diver ascends rapidly, the decrease in pressure can lead to the formation of bubbles in the bloodstream and tissues, causing decompression sickness, also known as "the bends." Symptoms can range from joint pain to more severe complications affecting the central nervous system or lungs.

In addition, a rapid ascent can cause lung expansion injuries. This occurs because the gases in the lungs expand as the surrounding pressure decreases. If the diver does not exhale appropriately during ascent, trapped air can expand and potentially rupture lung tissues, leading to serious complications.

Understanding this principle emphasizes the importance of controlled ascents, utilizing safe ascent rates and safety stops to avoid these significant risks, ensuring divers can safely return to the surface without adverse health effects.