Abstract: A ventilation device is disclosed for covering duct openings in the floor or wall of a building or other unit containing heating/cooling ductwork. The device includes a ventilation cover member sized and shaped to cover the duct opening of a building heating/cooling ductwork system. The cover member has a peripheral portion overlapping the duct opening, an outer face, an inner face, a central opening to permit airflow through the cover member, and a plurality of depending edge elements that engage the interior periphery of the duct opening. A filtration basket is provided and has a plurality of spaced peripheral side panels, a bottom panel and an open upper end portion. An attachment member is disposed about the peripheral side panels proximate the upper end portion and is adapted for securing the open end portion of the basket to the cover member depending edge elements. The basket is sized and shaped to project into the duct opening.