The door type louver return air outlet adds a frame, a specially designed door lock, and a chain on top of the fixed one, which is conducive to installation and cleaning of the filter screen. When in use, gently tap the door bolts on both sides of the valve by hand to open the valve. When pulling out the filter screen, simply push the valve up, and the two spring door locks will automatically lock. It is commonly used for return air outlets in guest rooms and halls.