Patients are being offered participation in this pirfenidone trial because They have been diagnosed with fibrotic hypersensitivity pneumonitis (FHP), a type of interstitial lung disease (ILD). This is a disease where scarring of lung tissue occurs as the result of inhaling substances called antigens. These antigens can be substances such as molds, chemicals or dust. As a result of this scarring the lungs are is not able to move oxygen into the bloodstream to reach other organs.