It's when you smoke. Smoking causes your air sacs ( littles sacs in your lungs to get bigger, decreacing the amont of surface area in your lungs) and making you unable to breathe and if you smoke too much you get Lung Cancer and you'll die.
A pathological diagnosis defined as the permanent destructive enlargement of the air spaces distal to the terminal bronchioles, resulting in loss of alveolar surface area and reduction of oxygen...