Inclusion Criteria:  Adult outpatient subjects (18 years old or older) that fulfill the 2020 ATS/JRS/ALAT diagnostic criteria of HP of at least moderate confidence (70% confidence or more). Willingness to undergo the evaluations proposed in this protocol HP diagnosis within the last 24 months Presence of radiological or histological fibrosis:  4.a. Radiological fibrosis consists of unequivocal fine or coarse reticulation with architectural lung distortion and/or traction bronchiectasis and/or honeycomb.  4.b. Unequivocal histopathological fibrosis evidenced on lung specimens  Exclusion Criteria:  Pregnancy Presence of established connective tissue disease Severe comorbidity impacting on the respiratory system as judged by the attending physician (ex. congestive heart failure, neoplasm, post-COVID-19 sequelae) Use of supplemental oxygen at rest Dyspnea mMRC 4 (too breathless to leave the house or breathless when dressing or undressing) Unequivocal emphysematous pattern of HP on HRCT Unequivocal pleuro-parenchymal fibroelastosis on the HRCT Significant pulmonary arterial hypertension:  8.a. Signs of right ventricular failure by echodopplercardiogram or 8.b. Cardiac index < 2L/min/m2 or right heart catheterism