The chamber has inlets (10,21) that are connected at the space. The inlets are formed on tube sections (30,40) that protrudes into the space of the chamber, tube section provided in longitudinal axis. The space of the chamber is partly filled up to a fluid level (50) with the fluid or with a mixture of the fluids in an operating condition. The inlets are located below the fluid level in the chamber. Independent claims are included for the following: (1) method of using venous chamber in blood treatment system and (2) blood tubing system.
