An air treatment system (100) is provided that comprises an air purifier (110) arranged to treat a first parameter of ambient air; a controller (130) arranged to control operation of the air purifier (110); and a sensor (120) arranged to detect a value indicative of the first parameter, and to output sensor data indicative of the value to the controller. The controller (130) is arranged to determine whether the sensor (120) and the air purifier (110) are in a same air space by controlling the air purifier (110) to operate in a test mode and analyzing sensor data from the sensor (120) received during the test mode. If the sensor (120) and the air purifier (110) are determined to be in the same air space, the controller (130) is arranged to control the air purifier (110) to operate in a mode based on sensor data from the sensor (120).