Blower Door and Duct Testing. 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. is the world's leading manufacturer of air leakage testing equipment.