Final answer:
When air collects in the pleural space surrounding the lungs is called pneumothorax.
Step-by-step explanation:
When air collects in the pleural space surrounding the lungs, it is called pneumothorax. The pleural space is the area between the visceral pleura (which covers the lung) and the parietal pleura (which lines the interior of the thorax). Normally, the pleural space contains a small amount of fluid that helps reduce friction as the lungs expand and contract. However, when air enters this space, it can cause the lung to collapse or deflate due to the increased pressure.