A pulmonary embolism occurs when a blood clot blocks an artery in the lung, usually starting in the deep leg veins. Symptoms include shortness of breath, chest pain, and fainting. Risk factors include a personal or family history of blood clots, smoking, obesity, oral contraceptive use, pregnancy, and certain medical conditions. Diagnosis involves blood tests and imaging scans of the lungs. Treatment focuses on blood thinners to prevent further clots while the body naturally dissolves existing ones. Regular exercise and compression stockings can help prevent pulmonary embolisms.