The funny thing about Duct Tape is we are NOT allowed to use it on any actual ducts. Every AIA(1) Specification (for commercial work) prohibits its use.
So the only thing we use Duct Tape for is wrapping bundles of Slip & Drive Cleats (the things that hold the joints of ductwork together) when we ship them to the job site in the truck.
I once ran into a tricky duct leakage problem ona Gubmint Project and found the solution in a then new Duct Sealant that was in 'tape form' that had a silver backing. At first the Gubmint guy went ape poop thinking it was Duct Tape. I had to submit all its spec's for Approval showing it was sealant before I could use it. Which finally came though and it did solve my problem.
Now that 'sealant stuff' (technical term) is so common it's sold at Home Depot. Next to the Duct Tape :-)
Sorry for the Tardy Reply but I was working, and on a (another) screwed up project with a STOO-PID™ deadline (nobody gives carp anymore, 'just get it done' -- sigh).
Today will get interesting when I start sending out emails.
(1) AIA = American Institute of Architects.