Adhesive tape is not designed to endure heat and extreme temperature fluctuations, making it an inappropriate choice for use in ducts. Over time, the adhesive in the tape can break down due to prolonged exposure to heat cycles. While duct tape is great for many purposes, such as wart removal, it should never be used to seal ducts. Some homeowners may attempt to seal air leaks with putty or metal tape and insulate ducts in the attic, mezzanines, basement, and garage as a DIY project.
However, adhesive tape is not suitable for use in air conditioning systems due to its performance issues and flammability. It also cannot stick to the ducts themselves, but will stick to the outer layer of dust. In general, codes forbid the use of adhesive tape in any hole, crack or hole in the air ducts. While general-purpose adhesive tape is not suitable for use in air conditioning systems, there are some fabric adhesive tapes that are specifically designed for certain HVAC applications.