Best sealing tape for metal duct seams

[Alan Lightstone]

I remeber reading years ago about a duct sealing method being invented at Lawence Berkely lab when I worked there. They sealed up all the registers of a house furnace duct system. Then they pumped in a special gas at low pressure. As it leaked out of joints it would turn into a solid and seal the leaks. It had to run for several hours I have no idea what vaporised the glue.
They do use pressurized smoke to find vacuum leaks in cars. Folks adapt those party fog machines to do this.
Bil lD

I saw a This Old House episode recently where they did this, so a version must be commercially available.

[Jeff Bartley]

Has anyone ever tried Zipp tape? I haven't used it on metal pipe but I did use it between my cyclone and the flex hose at the bottom of the cyclone.....for that it worked great.

[roger wiegand]

Duct tape that's ASTM rated for ductwork works well, lasts for decades, and is relatively easy to remove as needed. You'll probably find it in the plumbing section and expect to pay $10 a roll or more, it's not the buck a roll stuff that's given duct tape such a bad name.

[Derek Meyer]

I saw a This Old House episode recently where they did this, so a version must be commercially available.

They have a variation on the technique that is used for sealing the whole house during construction. It can be done either just before insulation or after drywall is hung and taped. They use a blower door to put the house under positive pressure and then spray the sealant in a very fine mist, which is carried through all the openings in the house and builds up on the edges, sealing them up. No idea on how much it costs but it is something I will be looking into the next time I build a new house.