Abstract: A system and method for measuring the airflow in an air handling unit, comprising a pressure plate with a plurality of apertures having a known surface area, a differential pressure manometer, and two. The first end of the leads is attached to a differential pressure manometer and second end of the leads is attached to the pressure plate. The pressure plate is placed in the filter rack of an air conditioning system the differential pressure manometer measures the differential pressure loss across the pressure plate allowing the user to determine airflow conditions and the location of obstructions. Additional embodiments of the system and method herein include placing two sensor tubes having apertures along the thereof at specific locations within the air handling unit that, when attached to a manometer, measure the differential pressure loss across the two locations. Various methods for establishing and monitoring proper airflow in an air handling unit are also contemplated.