The hinged louver return air outlet is an additional inner frame on the basis of the LFK-3 type air outlet. The whole air outlet is in the form of a valve. The return air of the room. The filter matched with this tuyere is fixed on the valve, therefore, the valve can be opened as long as the latches on both sides of the valve are gently pushed by hand, and the filter can be pulled out from the valve; The door bolt can be automatically locked, and the appearance is smooth.