While air may enter the mediastinum from several sources such as esophagus, the neck, or retroperitoneal injuries, most commonly traumatic pneumomediastinum results from air tracking back to the mediastinum from a bronchial injury along the bronchial tree. Even in the absence of trauma, pneumomediastinum may develop after coughing, forceful inhalation/exhalation, or esophageal rupture. Mediastinal air rarely causes a problem itself but signifies potentially more serious injuries of the tracheobronchial tree or the esophagus. Penetrating injuries of the mediastinum, especially high-energy gunshot wounds, will often leave a “track” of metallic fragments, bone, blood, and air making injured structures easier to identify. Compared with low-energy knife wounds, GSWs create a larger track of hemorrhage. The termination of the wound may be the presence of the bullet or the exit site from the body but the extent of a knife wound may not be so obvious. For this reason, delayed complications from chest stab wounds are well recognized.