An ionizing device is described, comprising a tubular bulb made of electrically insulating or dielectric material extending along a longitudinal reference axis and having the two longitudinal open ends and opposite each other, a tubular cathode engaged in the bulb, a tubular anode fitted to the bulb, a pair of covers, each of which has a respective internal seat into which a respective end of the bulb is inserted so as to hermetically seal it, and a conductive electrode which extends into the bulb and is electrically connected to the cathode.