Emphysema is a disease of the lungs. It is caused by a chemical imbalance, caused from smoking in most cases, that leads to the over-inflation of air sacs (alveoli) in the lungs. Alveoli are responsible for transferring oxygen in the air into the blood. Damage to them is irreversible and results in permanent "holes" in the tissues of the lower lungs. The damaged alveoli cause a shortness of breath. People with emphysema have a hard time exhaling and normally have trouble performing their daily activities such as a short walks because they get out of breath so easily. In extreme cases the person has to carry around an oxygen tank with them to aid in breathing.

Every smoker will eventually develop emphysema if they smoke long enough. Emphysema is caused by years of exposure to irritating fumes and air pollution, the main cause being smoking.  Symptoms include shortness of breath, a chronic cough, bluish skin color, wheezing, dizziness, stress, impotence, fatigue, impaired ability to concentrate, and difficulty falling asleep.