This research project, funded by the Canada Mortgage and Housing Corporation is a first attempt to validate a method using intensimetry to measure the sound power levels generated by fans when they are connected to the ductwork of a ventilating system, and operating in real conditions. The goal of the study was to determine the accuracy and limitations of the proposed method. To achieve this, the results of the measurements made according to the proposed procedure were compared with those obtained in a reverberant room using the method described in the AMCA 300 standard. All the measurements were conducted in the acoustical laboratories of the National Research Council of Canada under the direction of Dr. A.C.C. Warnock and the author.