A cooling system, e.g. for a hot aisle/cold aisle datacenter system, can detect local pressure differences between the hot and cold aisle by way of a conduit containing a temperature sensor positioned between the hot aisle and cold aisle. The temperature sensor can detect a temperature of airflow between the aisles by the temperature sensor in the conduit. This conduit is defined by a frame or insert that includes a first opening and a second opening separated by a nonzero distance and that is configured to penetrate a containment element separating the hot aisle and cold aisle. The cooling system can, based on the interstitial temperature, determine a direction of flow of the airflow between the hot region and the cold region and detect recirculation between the hot region and the cold region based on the direction of flow.