A system and device for monitoring pressure in a blood line. In such device, a pressure transducer line branches off a blood line to enable the connection of a pressure transducer. To avoid any contamination of the pressure transducer, a first pressure transducer protector filter is used that divides the pressure transducer line into a blood line section between the blood line and the filter, and a pressure transducer section between the filter and the pressure transducer. A sensor is provided for detecting the presence of liquid in the pressure transducer section of the pressure transducer line so as to provide a system by which an unnoticed failure of the first pressure transducer protector filter in a pressure transducer line is avoided as well as a device that can easily be re-used.
