I was wondering what are the causes of pneumothorax?

Most common causes: Rupture of pulmonary bleb , chest trauma and iatrogenic caused by various surgical procedures, including endotracheal anesthesia , ventilators etc

Many: A pneumothorax is a collapse of the lung in the chest space due to air escaping the lung. It can be from penetrating trauma, such as a stab wound or gunshot wound. They also can be complications of procedures, such as removal of fluid from around the lung or placement of a central line. But, many times, it can be from a rupture of a bubble that was present in the lung since birth.