A ventilation and fire extinguishing device for electrical panels, comprising; a box-like metallic base (10), which is placed on top of an electrical panel and which has at least one lower opening (11) through which flows an air or heat flow (F) coming from said electrical panel, and at least one sheet or laminar plastic element (12) placed on top of the boxlike metallic base (10); a hinged flap (13) is created in element (12), so that at least one portion of the perimeter of flap (13) is made in one piece with element (12) and constitutes a linear fold (16) of element (12), suitable to allow said flap (13) raising and lowering with respect to element (12) for opening and closing a corresponding upper opening (15) in element (12) which is defined by said flap (13). In normal circumstances the flap (13) willfunction as a gravity operated ventilation flap, however in case of an internal fire the heatflow will cause the linear fold (16) to buckle and the flap will close the opening (15) in order to extinguish the fire due to the lack of avialable fresh oxygen in the electrical panel.