Abstract: A blood filter is disclosed which actively removes unwanted particles from the blood without using passive elements such as a cartridge. The blood filter includes a housing having a blood inlet area for receiving blood to be filtered, a blood outlet area for providing filtered blood to a patient, and a blood return area for returning blood having unwanted particles to a reservoir. A plurality of independent blood paths extend from the inlet area to the outlet area of the housing for separate flows of blood therethrough. An array of detectors is placed adjacent the exterior of each blood path for detecting unwanted particles in the blood flowing therethrough. An array of valves is placed in operable relationship with the blood paths to close selected ones of the blood paths when unwanted particles are detected. Blood return conduits open to divert the particle-containing blood to a reservoir. Several arrays of detectors and valve combinations may be provided for redundancy.