A normal flow volume loop has a rapid peak expiratory flow rate with a gradual decline in flow back to zero. The inspiratory portion of the loop is a deep curve plotted on the negative portion of the flow axis. Inspiratory data is often overlooked, but the flow volume loop gives the opportunity of assessing this information as well.

The normal volume time curve has a rapid upslope and approaches a plateau soon after exhalation. The maximum volume attained represents the forced vital capacity (FVC), while the volume attained after one second represents the forced expiratory volume (FEV1).