The primary diagnostic tests are FEV1: The volume of air forcefully expired during the first second after taking a full breath Forced vital capacity (FVC): The total volume of air expired with maximal force Flow-volume loops: Simultaneous spirometric recordings of airflow and volume during forced maximal expiration and inspiration Reductions of FEV1, FVC, and the ratio of FEV1/FVC are the hallmark of airflow limitation.