Abstract: A gas mask is provided which includes a facepiece including a front portion of semi-rigid rubber highly resistant to chemical agents and a sealing skirting of soft rubber having a high mechanical resistance, co-vulcanized with the front portion of the facepiece. A nozzle, connected to a half mask situated inside the facepiece, is tightly fastened to the front portion of the facepiece. An inflow opening and an outflow opening are provided which are substantially coaxial and are located in the lower portion of the nozzle. The inflow opening places the interior of the facepiece into communication with the external atmosphere and the outflow opening places the interior of the half mask into communication with the external atmosphere through an inflow chamber and an outflow chamber which are separated by a partition. The inflow chamber communicates bilaterally with a space located between the half mask and the facepiece.