Duct Testing Systems Blower Door and Duct Testing Equipment are designed to identify air leakage in a home, building, or facility. Air leakage in a home, building, or facility can increase heating and cooling costs dramatically and cause problems with comfort, moisture, and health. While the technology has been around for many years , it is still not yet commonplace, so there is great opportunity for contractors who want to add this service to their capabilities. Retrotec Inc. and TSI/Alnor are leading manufacturers of air leakage testing equipment.