Yeah, one would think so. But, it isn't good for ducts. It's also called "gaffer's tape".
There is a foil tape that is actually designed for ducts.
That's the stuff.
Fabric based Duct tape dries out in time so air leaks occur so it doesn't cut the mustard as the saying goes.
(
Anyone care to explain that saying?)
Guess you can always use duct tape to kidnap someone or to truss your roast duck if you don't mind the taste of glue.
I am a licensed contractor and I can assure you that duct tape is used for taping ductwork.
Now, professionals do not use the cheap colored tape thats sold in "Dollar General". But they do use duct tape as its much cheaper than foil tape.
There are many brands and good quality commercial grade duct tape is available and used by HVAC contractors every day.
In fact all my duct work here in my house is fabric based commercial duct tape.
These fabric tapes are "listed" for the purpose and if they were not, they would not pass inspection.
I personally keep a roll of foil tape around. Should I ever need to seal a duct, I would use it.
But to say duct tape is not for ducts would be wrong. But it must be listed for the application.
Foil tape is very expensive and many contractors just will not use it unless the customer is willing to pay more for it.
They also paint a sealer on the joints when complete in many cases. This eliminates the need for foil tape.
It also should be noted that some duct work is flexible and requires a certain tape be used with it. Mostly a gray colored fabric based duct tape listed for the application.
Metal duct work is a good application for foil tape. But there is no requirement for its use.