Air conditioning system for conditioning an air flow guided in a duct for the air conditioning of a room, comprising - a fan unit, - an air conditioning device for varying the physical parameters of the air, namely temperature and/or humidity, - wherein the air conditioning device is designed, on the one hand, so that the air flow can flow through it and, for this purpose, comprises a plurality of air-flow ducts, wherein the air-flow ducts are defined by sheet-metal layers which are arranged parallel to one another and are in each case aligned parallel to the flow direction of the air flow, and, on the other hand, comprises heat- or cold-transfer means for applying heat or cold to the air-flow ducts, wherein the air conditioning device is designed as a contiguous component for multifunctional operation and the multifunctional operation comprises at least one heat dissipation operating state, e.g. cooling of the air flow (cooling operation) and/or dehumidification of the air flow (dehumidifying operation), wherein a nozzle assembly having a plurality of nozzles, which are arranged distributed over the cross-section of the duct and are acted upon by pressurized water, for the delivery of water, in particular in the form of a spray mist, is arranged upstream of the air conditioning device at a spacing opposite the direction of flow by a free humidifying section, characterized in that the multifunctional operation comprises at least one heat supply operating mode including a sterilization operation by means of drying humidified or wet surfaces, wherein the air conditioning device is heatable to a sterilization temperature for drying the air conditioning device, and the fan unit is adapted, in one operating mode, to discharge the air humidified by the sterilization step into the room and, in a reversed operating mode of the fan unit, to discharge the humid air out of the building against the normal direction of flow of the air flow, and, additionally, for example - post-evaporation of humidifying particles entrained in the air flow (humidifying operation) and/or - heating up the air flow (heating operation). - a fan unit, - an air conditioning device for varying the physical parameters of the air, namely temperature and/or humidity, - wherein the air conditioning device is designed, on the one hand, so that the air flow can flow through it and, for this purpose, comprises a plurality of air-flow ducts, wherein the air-flow ducts are defined by sheet-metal layers which are arranged parallel to one another and are in each case aligned parallel to the flow direction of the air flow, and, on the other hand, comprises heat- or cold-transfer means for applying heat or cold to the air-flow ducts, wherein the air conditioning device is designed as a contiguous component for multifunctional operation and the multifunctional operation comprises at least one heat dissipation operating state, e.g. cooling of the air flow (cooling operation) and/or dehumidification of the air flow (dehumidifying operation), wherein a nozzle assembly having a plurality of nozzles, which are arranged distributed over the cross-section of the duct and are acted upon by pressurized water, for the delivery of water, in particular in the form of a spray mist, is arranged upstream of the air conditioning device at a spacing opposite the direction of flow by a free humidifying section, - post-evaporation of humidifying particles entrained in the air flow (humidifying operation) and/or - heating up the air flow (heating operation).