The device comprises a container (1) of active substance in liquid form, which is sealed by means of a permeable membrane (3) which lets the active substance vapour pass and prevents the passage of liquid, being completed with a porous support (5) on the inner face of the membrane (3), so as to take the active substance to the centre of the membrane (3), this being warmed by a heater element (9) with pins (10) which are coupled directly onto the pins (8) of a socket plug (7), via which the device is powered, so that the evaporation of the active substance takes place by warming and it issues to the exterior by ways of slots (12) provided in a housing (11) which joins the container (1) to the socket plug (7). The assembly forms a disposable device, although the container (1) can be embodied so that it is interchangeable.