A pneumothorax occurs when air leaks into the space between the lung and the chest wall, causing the lung to collapse. This can happen due to injury, such as a broken rib, or spontaneously without any obvious cause. Symptoms may include sudden chest pain and difficulty breathing. Treatment for a pneumothorax often involves monitoring the condition, but in more severe cases, a doctor may need to remove the air using a needle or chest tube. Most people recover fully, but it is important to seek medical attention if symptoms arise.