Abstract: A centrifugal blower impeller for a vehicle heating and ventilation system has a central hub, a peripheral crown having a set of vanes for drawing the air axially through the crown, to deliver the air radially towards the outside, and a set of arms, spaced apart at regular intervals and joining the hub to the crown. This set of arms defines a generally concave bowl-shaped envelope, with the arms being joined to the hub in the center of the bowl and with the crown at its periphery. At least some of the arms have reinforcing ribs close to the junction between the arm and the hub. Each rib lies in an axial plane and is on the side of the arm corresponding to the concavity of the bowl.