Abstract: A method and apparatus for testing the effectiveness of a building air barrier, or part thereof, whereby an identification of any air leakage therethrough is provided. A soap solution (or other solution having a similar bubbling characteristic) is applied to a selected air barrier test area. An open-ended flask is positioned over the test area and a centrifugal (or standard) fan is activated at the head of the flask to create an air pressure differential across the air barrier. In the presence of the air pressure differential the soap solution will bubble if there is an air leakage in the air barrier within the test area and, therefore, the existence or non-existence of bubbles in this area identifies whether or not there is an air leakage (i.e. break) in the air barrier in that area.