Mold in Ductwork: A Forensic Analysis

Mold growth in ductwork is an abnormal, but not an unusual condition. One of the prerequisites for mold growth to occur is that the interior surface of the duct must become wet. Moisture in ductwork can occur for a number of reasons, including, but not limited to: water can be stripped off cooling coils and carried down the ductwork; operation of the equipment can result in condensation inside the ductwork; or, a fog could be created inside the duct. This paper will describe the causes of moisture inside ductwork, the factors allowing mold growth to occur, and strategies to correct or avoid these problems. After the moisture problems are resolved, mold will cease to grow; but microbiological debris will be left in the ducts. The pros and cons of duct cleaning to deal with this debris, as well as alternative duct cleaning methods, will also be discussed.