Originally Posted by DL4EVR
My question is, if you're going to have to take your shoes off anyway when you go through the detector, what's the point of going through the puffer to begin with??
The puffer would show if you have been in the presence of explosives even if you werent carrying any through.
My guess is that they scan the shoes since it would be possible to hide something (small but sharp) or even a small amount of explosive in your shoes and get it through the puffer.
The puffer can only detect something if the puffs of air can dislodge the necessary particles from your clothing. The puffer cannot detect something if you have been extremely meticulous about cleaning up after inserting explosives in your shoes ... as an example ...