Non Critical Airflow uses a damper, usually a simple blade or opposed blade dampers, where up to 50% of the airflow happens in the first 10% of the damper stroke.

Control “Valves” are used in critical applications for their linear flow characteristics, as it is important to control across the entire range of the valve operation.
Low Pressure Drop Lab Control Valves
We were first attracted to the AccuValve & Pnuemavalve because of their low pressure drop, linear control. When added to the accuracy of the Vortex Airflow Measurement, and the fast response of the Belimo or Pnuematic accuators, it is the complete package for the control and measurement of airflow.