The amount of air can be measured by its volume or by its mass. Typically it is measured by volume, but for some applications it is necessary to measure it by mass, as air is a gas and therefore its volume can vary with temperature.
Typical units to express airflow are:
By volume 
By mass 
The instrument that measures airflow is called an airflow meter.
The equipment that regulates the airflow is called a damper. The damper can be used to increase, decrease or completely stop the flow of air. A more complex device that can not only regulate the airflow but also has the ability to create an airflow is an air handler.
See also 
- "OMEGA ENGINEERING - Flow Control". Omega.com. 1984-11-21. Retrieved 2012-04-24.
- Fluid Volumetric Flow Rate - Fluid Flow Hydraulic and Pneumatic, Engineers Edge, retrieved 9 January 2012
- "Airflow Unit Conversion". Comairrotron.com. Retrieved 2012-04-24.