The paper presents the assessment of electromagnetic compatibility of adjustable drives used in residential air conditioning systems (i.e. air handling units, systems that conserve a significant amount of energy, while maintaining indoor comfort) with a particular stress on brushless DC motors. In the introductory section, a recall of the new smart power modules, that drive centrifugal fans provided with brushless DC motors are briefly depicted. Next, the main operating principles of air handling units are shortly addressed, along with detailed test setups and results obtained on conducted electromagnetic interference and electromagnetic conducted immunity, according to electromagnetic compatibility standards, compulsory for air handling units. The main conclusion of the paper is that even if electromagnetic compatibility tests are quite tedious and time consuming and particularly more often neglected, they have to be a permanent concern from the early stage of design, in order to save other resources which would be involved with certitude afterwards, in the final stage of a project.