Can confirm.

I was "digitally sniffed" for explosives once at an airport in Florida about 3 years ago.

They took a piece of what looked like tissue (probably an odorless control) and rubbed it inside my backpack.

They then placed that "tissue" into a very large machine (half the size of the man performing the procedure) which I assume smelled it for explosives.

After standing there for about 30 seconds staring at the machine, I was told I was free to proceed into the secure waiting area.