A ventilation unit for an electrical enclosure, comprising a fan (VENT) and a housing which comprises a base and a cover assembled on the base, in which the housing has the shape of a right block with a square base, four side faces and a top face, in which said base comprises a bottom wall forming said base of the housing and a side wall following the four side faces of the housing, an opening made through its bottom wall and a seat made around its opening and housing the fan, in which the cover is affixed to the base and comprises the upper face of the housing, and in which, along each side face, the side wall of the base comprises a first grid, characterised in that, along each lateral face, the ventilation unit comprises a second grid mounted so as to pivot between: - a closed position, in which the second grid covers the first grid of the corresponding lateral face, being folded against this first grid, so that the ventilation unit has a first configuration defining a first protection index of the ventilation unit, and - one or more open positions, in each of which the second grid is raised with respect to the first grid of the corresponding side face, being pivoted at a determined angle of inclination which is non-zero, so that the ventilation unit has a configuration which is different from the first configuration and which defines a protection index of the ventilation unit, different from the first protection index. in which the housing has the shape of a right block with a square base, four side faces and a top face, in which said base comprises a bottom wall forming said base of the housing and a side wall following the four side faces of the housing, an opening made through its bottom wall and a seat made around its opening and housing the fan, in which the cover is affixed to the base and comprises the upper face of the housing, and in which, along each side face, the side wall of the base comprises a first grid, characterised in that, along each lateral face, the ventilation unit comprises a second grid mounted so as to pivot between: - a closed position, in which the second grid covers the first grid of the corresponding lateral face, being folded against this first grid, so that the ventilation unit has a first configuration defining a first protection index of the ventilation unit, and - one or more open positions, in each of which the second grid is raised with respect to the first grid of the corresponding side face, being pivoted at a determined angle of inclination which is non-zero, so that the ventilation unit has a configuration which is different from the first configuration and which defines a protection index of the ventilation unit, different from the first protection index. - a closed position, in which the second grid covers the first grid of the corresponding lateral face, being folded against this first grid, so that the ventilation unit has a first configuration defining a first protection index of the ventilation unit, and - one or more open positions, in each of which the second grid is raised with respect to the first grid of the corresponding side face, being pivoted at a determined angle of inclination which is non-zero, so that the ventilation unit has a configuration which is different from the first configuration and which defines a protection index of the ventilation unit, different from the first protection index.