Abstract: A system for selectively opening and closing a ventilation opening in a window glass panel. The system includes a shield gasket and a ring-shaped fixing frame inserted into the opening, with the gasket interposed between the opening and the fixing frame. A cover is inserted into the fixing frame to open and close the ventilation opening. Fixing frame alternatives include wherein the fixing frame comprises a drain structure, an exterior gutter, a filter, and peripheral elastic support hooks. Shield gasket alternatives include wherein a body part transforms into a cylindrical shape during installation of the fixing frame, and wherein a wall part comprises a circumferential elastic protruding part forming an inner space part therein. Cover alternatives include wherein the cover includes ring shaped shielding walls and a hook to engage fixing frame insertion groove.