Duct tape is quite a useful tape and good for many things. It was even used for some repairs on by astronauts on Apollo 13 to get home to Earth.[reference]
However, duct tape is not good on ducts. It is called “duct tape”, because they colored it to match the color of ducts. But it did not do a good job of sealing ducts. This was determined in a study in 1998 by Max Sherman and Iain Walker of the Department of Energy’s Lawrence Berkeley National Laboratory where …
“We tried as many different kinds of duct sealants as we could get our hands on. Of all the things we tested, only duct tape failed. It failed reliably and often quite catastrophically.” said Sherman [reference]