Abstract: A two-stage electrostatic filter is provided for air recirculation units. The filter includes at least one ionization stage (100) formed by parallel facing walls, in which a high-potential electrode (50) is located, and at least one precipitation stage (200) formed by parallel walls of negative potential in relation to the ionization stage. The ionization and precipitation stages-include at least one inverted U-shaped cathode (10), the opposite ends of which are mechanically and electrically integral with a transverse supporting section (20) and within which is provided at least one baffle (10b) extending parallel to outer arms (10a) of the U-shaped cathode, but with a height lower than that of the arms. The cathode (10) cooperates with a U-shaped anode (30; 1030) counterposed thereto and rendered mechanically integral by insulated supports (40). There are also provided further cathodes (110b; 2110b) for the modular expansion of the filter in the direction of its width.