[chriskanan]

I did some work during my PhD on recognizing scenes from electronic-nose data. The problem is more on the hardware side of things than the algorithm side of things. Today's electronic noses are still pretty large devices in which a sample needs to be placed within the device. Unless the state-of-the-art has advanced significantly in the past 3 years, none of them are like wielding an artificial nose on a stick that you can just wave around sniffing things.

[GigabyteCoin]

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.

[mahyarm]

Those are things similar to a mass spectrograms. The tissue picks up particles, and is then analyzed by the machine to create a mass spectrogram of the napkin. If it contains masses similar to explosive powder residues, then you're in trouble.