Emphysema is a chronic obstructive lung disease in which alveoli fail to recoil properly and do not expel enough air. In long term cases, alveoli deteriorate due to inflammation, their walls harden with connective tissue deposition (above) and alveolar capillaries are damaged. The likelihood of emphysema increases with factors that predispose to chronic inflammation eg. air pollution, inhalation of dust, soot and/or solvents. Smoking is a common cause of emphysema.