Pulmonary fibrosis is a lung disease that occurs when lung tissue becomes damaged and scarred. This thickened, stiff tissue makes it more difficult for your lungs to work properly. Pulmonary fibrosis (literally "scarring of the lungs") is a respiratory disease in which scars are formed in the lung tissues, leading to serious breathing problems. It might be caused by breathing in wood or metal dust at work or home, Having acid reflux disease or smoking cigarettes.There are many forms of pulmonary fibrosis i.e., idiopathic pulmonary fibrosis, idiopathic nonspecific interstitial pneumonia (NSIP), Cryptogenic organizing pneumonia (COP), Sarcoidosis etc.