How does gas get "off gassed" during a diver's ascent?

During a diver's ascent, gas is "off-gassed" primarily due to the reduction in ambient pressure as the diver rises towards the surface. When a diver descends, inert gases such as nitrogen are absorbed into the body's tissues under higher pressure conditions. As the diver ascends, the pressure around them decreases, and the body can no longer hold these gases in solution with the same efficiency.

Off-gassing occurs as these gases are expelled from the body's tissues back into the bloodstream and ultimately expelled through the lungs during exhalation. This process is crucial for preventing decompression sickness, as ascending too quickly can lead to the formation of bubbles in the bloodstream, resulting in serious health risks.

The other options do not accurately represent how off-gassing occurs. For example, gas absorption by the lungs does not facilitate the release of gases during ascent; instead, it's the pressure change that enables this process. Uncontrolled ascent can exacerbate the risks associated with off-gassing by not allowing sufficient time for safe gas release. Maintaining pressure would prevent the necessary change for off-gassing to take place. Finally, breathing a high oxygen environment doesn't directly relate to the off-gassing of inert gases accumulated during a dive.