Adjustable slots provide airflow distribution and are preset by the installer.
They should not be adjusted by the users. Airfoils Airfoils are usually on the lower front and the sides of the hood. They permit air to flow smoothly into the hood and prevent turbulence which can cause contaminants to escape into the room. The bypass grille at the top of the hood opens as the sash is lowered to ensure that face velocity of the air through the sash opening is not excessive. The rear baffle permits an even distribution of air in the hood.