Adjustable air – flow switch from AVFS can replace instruments that are from Dwyer. This is a kind of switch that is designed specifically for monitoring the ducts that are meant for air flow and also can provide output of 3A for indicating loss or change in flow. The device can be used for showing normal status, one needs to turn on the fan or the unit of air handling. AVFS can be activated by altering damper or by decreasing the speed of the fan. This device can indicate when there is loss in flow. There are various colors of LED indicators available for showing different status.