Abstract: A length of duct is provided for seating a portable airflow meter so that when the end of the duct away from the airflow meter is put over a part of a ventilation opening, airflow can be measured in a manner not subject to substantial errors from the presence of jets or eddies in the flow of air out of the ventilation opening. The lower part of the shroud has a flat, perforated baffle plate disposed horizontally near the bottom in the center of the duct and at a distance farther towards the middle of the duct, and evenly spaced set of downwardly pointing triangles extending obliquely from the respective middles of the duct wall and a more numerous set of upwardly extending oblique members having the shape of short angle bars, tapering slightly. Facing the front and back of the airflow meter are cutouts in the upper end of the shroud so that measurements of air flowing into the ventilation opening will be equivalent of those that would be made without the shroud.