In refineries, flow nozzles are used, for example, to measure the volume flow of steam flows that, under high pressure, escape into the atmosphere. For the monitoring of coolant circuits, calorimetric flow switches with integrated LED displays are suitable. The measurement of volume flows in ventilation pipes in air-conditioning technology is carried out by compact air flow meters with electrical output signals. The exact control of the room air supply is used for energy-efficient air conditioning in accordance with applicable EU standards.