Abstract: The present invention concerns a procedure and apparatus for controlling and maintaining air currents or equivalent in an air-conditioning installation or equivalent. The air-conditioning installation comprises one or several air-conditioning machines (P) for producing the desired flows, and one or several duct systems for conducting the flows into the desired room spaces (H.sub.1,H.sub.2 . . . ) or equivalent and/or out from the room spaces (H.sub.1,H.sub.2 . . . ) or equivalent. The duct systems consist of requisite trunk, zone and room duct systems (R,Z,C). In the procedure the air flow rates required at any given time in the air-conditioning system are determined on the basis of the air temperature and/or air quality and/or air noise levels and/or air pressure conditions and/or other similar factors. On the basis of the respective air flow rates determined by calculation, a combination of the set values for all control members (S.sub.1,S.sub.1.1,S.sub.1.2 . . .