It is a simple office-based test to assess lung function. The patient breathes into a tube attached to the spirometer, in a rapid and sustained manner. Spirometry test measures how much and how quickly a person can blow out air. It is usually done to diagnose various lung conditions including Asthma, COPD, Pulmonary fibrosis (Interstitial lung disease-ILD), Occupation related lung disorders, Neuromuscular disorder. It is also done prior to a major surgery- to assess risk of pulmonary complications. Patients with a chronic lung disorder may require periodic testing to assess progression of the disease and response to treatment.