A ventilation system includes a blower wheel (1) and a drive motor (9) with an external rotor (9b). The blower wheel (1) includes a central part (3) having a cylindrical wall (11) and defines a housing (13) to house the external rotor (9b). The blower wheel (1) further includes a frontal wall (15) comprising an opening (17) so as to exhibit a degree of openness that is greater than a predefined degree of openness.