Flow switches are devices used to monitor the flow of liquids or gases in a pipeline or duct. They work by detecting changes in the flow rate and sending a signal to a control system to indicate a change in flow. Flow switches are commonly used in HVAC, water treatment, chemical processing, and oil and gas, among others, to monitor and control the flow of liquids or gases. They are typically designed and tested to meet industry standards and regulations to ensure accuracy, reliability, and safety.