2012 Buick Verano Owner Manual - Page 200

8-6 Climate Controls Air Vents Use the louvers located on the air vents to change the direction of the airflow. Use the thumbwheels near the air vents to control the amount of airflow or to shut off the airflow. Operation Tips . Keep all outlets open whenever possible for best system performance. Keep the paths under all seats clear of objects to help circulate the air inside the vehicle more effectively. Use of non-GM approved hood deflectors can adversely affect the performance of the system. . .