Airflow is defined simply as the movement of air through an HVAC system.

Typically, airflow is measured in CFM or L/S (cubic feet per minute or Liters per second). It is also sometimes measured in air changes per hour (or ACH).

The amount of airflow delivered to a space is determined based on the design load of the space and sometime the airflow may vary based on the current load of the zone (for example, in VAV systems)