I。 Pneumonia 肺炎 Pneumonia can be very broadly defined as any infection in the lung Classification It is best to classify pneumonias either by the specific etiologic agent( Air containing hazardous dusts, chemicals and microorganisms )or, if no pathogen can be isolated, by the clinical setting in which infection occurs.12 I. Pneumonia 肺 炎 Pneumonia can be very broadly defined as any infection in the lung Classification: It is best to classify pneumonias either by the specific etiologic agent ( Air containing hazardous dusts, chemicals and microorganisms ) or, if no pathogen can be isolated, by the clinical setting in which infection occurs