The present invention relates to a method and a device for providing clean air in premises, wherein impure air is received or taken in into an air treatment device (1) from lower portions of the premises and cleaned or purified therein. A first partial flow (DS1) of air received or taken in into the air treatment device (1) is cooled, while a second partial flow (DS2) of air received or taken in into said air treatment device (1) is heated. The cooled air (KL) in the first partial flow (DS1) is brought to flow, through at least one cell body member (17) in at least one air discharge unit (15), slowly downwards without substantial co-ejection of surrounding air to define at least one zone of clean air (RZ) in the premises beneath the air discharge unit (15). The heated air (VL) in the second partial flow (DS2) is discharged, through an air discharge opening (16), in an upwards direction such that said heated air (VL) rises in the premises at low speed. |