Pulmonary contusion is the most common injury found in blunt chest trauma, occurring in 25–35% of cases. It is usually caused by a collision while moving quickly. About 70% of cases result from motor vehicle collisions, most often when the chest strikes the inside of the car. Falls, assaults, and sports injuries are other causes. Pulmonary contusion can also be caused by explosions. The organs most harmed by blast injuries are those that hold gas, such as the lungs. Blast lung is severe pulmonary contusion, bleeding, or edema with damage to alveoli and blood vessels, or a combination of these. This is the usual cause of death among people who initially survive an explosion. Unlike other causes of injury in which pulmonary contusion is often found with other injuries, explosions can cause pulmonary contusion without damage to the chest wall.