An anti-pollution economiser device for fluid fuels, of the type comprising a conduit which may be coupled along the fuel supply pipe to form an integral part of the supply line and comprising an electromagnetic field generator which affects the fuel flowing inside the conduit from its inlet to its outlet, and comprising at least one channel forming an aeration chamber in open communication with the outside environment and made or positioned between the electromagnetic field generator and the conduit in which the fluid flows, said channel extending between the inlet and the outlet of the conduit so as to form a gap between the conduit and the electromagnetic field generator of the device, characterized in that it comprises: - a hollow cylindrical body closed at its ends by a flange or head and having a central/axial hole for the transit of the inlet and outlet ends, respectively, of the conduit positioned coaxially to the hollow cylindrical body, for the inflow and outflow of the fluid fuel into and out of the device, the ends of the conduit being fixed to the heads and by means of devices and designed to allow their fixing to the fuel supply line from a tank to an internal combustion engine, so as to form an integral part of the line; - the electromagnetic field generator consisting of solenoids with a substantially cylindrical extension, positioned inside the hollow cylindrical body and insulated from it, enveloping the conduit coaxially to the hollow cylindrical body, the solenoids powered with continuous current and being able to produce an electromagnetic field in the same direction as the fuel flow; - the channel positioned between the conduit and the solenoids constituting the electromagnetic field generator, with an inside diameter greater than the outside diameter of the conduit and the ends of which are fixed to the flanges or heads and for closing the hollow cylindrical body of the device, the channel having an inside diameter such as to create the gap between the conduit and the electromagnetic field generator; - the heads and for closing the hollow cylindrical body of the device being equipped with at least a first duct open towards the outside and in direct communication with the gap between the conduit and the electromagnetic field generator; - the inside of the conduit being made in such a way as to create a sort of undulating labyrinth-like path for the fuel which is repeatedly diverted relative to the longitudinal axis of the conduit of the device. - a hollow cylindrical body closed at its ends by a flange or head and having a central/axial hole for the transit of the inlet and outlet ends, respectively, of the conduit positioned coaxially to the hollow cylindrical body, for the inflow and outflow of the fluid fuel into and out of the device, the ends of the conduit being fixed to the heads and by means of devices and designed to allow their fixing to the fuel supply line from a tank to an internal combustion engine, so as to form an integral part of the line; - the electromagnetic field generator consisting of solenoids with a substantially cylindrical extension, positioned inside the hollow cylindrical body and insulated from it, enveloping the conduit coaxially to the hollow cylindrical body, the solenoids powered with continuous current and being able to produce an electromagnetic field in the same direction as the fuel flow; - the channel positioned between the conduit and the solenoids constituting the electromagnetic field generator, with an inside diameter greater than the outside diameter of the conduit and the ends of which are fixed to the flanges or heads and for closing the hollow cylindrical body of the device, the channel having an inside diameter such as to create the gap between the conduit and the electromagnetic field generator; - the heads and for closing the hollow cylindrical body of the device being equipped with at least a first duct open towards the outside and in direct communication with the gap between the conduit and the electromagnetic field generator; - the inside of the conduit being made in such a way as to create a sort of undulating labyrinth-like path for the fuel which is repeatedly diverted relative to the longitudinal axis of the conduit of the device.