An air processing system comprises an air purifier (10) and/or an air quality sensor (12). One or both is controlled (14), or else sensor information is interpreted, in dependence on activity status information received from a plurality of home appliances (16, 8, 20, 22). This enables the operational life time of components in system to be extended, specifically the sensors and/or air purifier filters. Alternatively or additionally, it enables the air quality sensor information to be interpreted more reliably.