The velocity of air moving through a fan system is expressed in which of the following units?

The velocity of air moving through a fan system is measured in feet per minute. This unit specifically reflects the speed at which air moves through the system, providing a direct measure of how quickly the air is traveling.

While cubic feet per minute is a measure of airflow and indicates the volume of air moving through a space over a minute, it does not express velocity. Gallons per minute and liters per second pertain to the flow rate of liquids, not air movement. Therefore, the use of feet per minute effectively captures the linear velocity of air in a fan system, making it the correct unit of measurement for this context.