Air flow meter is know as air consumption meter. It is a device that measures how much air is flowing through a tube. They does not measure the volume of the air passing through the tube, it measures the amount of mass flowing through the device in a defined time segment. This is just an application of mass flow meters for a special medium.
Air Flow Switch is designed to prove airflow control in wide variety industrial applications. An air flow switch is used as a volume booster, using a low flow pneumatic signal to produce an output pressure with a higher flow capacity. The air flow switch is available for either positive or negative air pressure. Air flow switch is also used to signal the air flow from ventilation units.