An extracorporeal blood circuit, comprising an expansion chamber for air-blood separation, wherein a filter (38) retains the solid particles in the blood. The filter has a trunco-conical filtering wall with a vertical axis surmounted by a top head (43) provided with upper openings (44) conformed and arranged such as to define a fluid passage which is asymmetrical with respect to the vertical axis. The top head does not retain air bubbles internally thereof, thus preventing a situation in which the air bubbles are directed towards an outlet of the expansion chamber and thus towards the patient. The extracorporeal circuit is used in a dialysis apparatus.
