This two-stage ejector comprises a body (16) comprising: - a compressed air intake (E); - a compressed air injection nozzle (17) placed downstream of the air intake; - a central duct (18); and - an outlet mixer (19). The injection nozzle (17), the central duct (18) and the outlet mixer (19) are disposed along an axis (X-X') of the ejector so that the ends of the axial duct are respectively spaced apart from the nozzle and from the mixer so as to form a first and a second suction zone (23, 25) that communicates with a single common air suction chamber (21).