Since HVAC systems are intended for long-term use within completed structures, they are often hazardous when placed in buildings under construction. When used during the construction phase, these systems are vulnerable to infiltration by a variety of harmful mold, bacteria, dust, debris, and other contaminants that can lead to health problems and other issues down the road. Further, designed to cool and heat occupants—not construction sites—these systems can create excessive moisture on the premises, wreaking havoc on materials.