Guardian™ Airflow Monitor senses and alerts the operator to low airflow conditions. From the monitor's face plate, the user can easily select and calibrate a set point between 30 and 250 fpm using a velocity meter and a screwdriver. Audible/visual alarm. Includes night setback, external alarm and alarm mute functions. Flush-mount design in Protector Premier, XStream and XL Fume Hoods. 115V 60Hz.