Comment by Teever

> This reminds me of the chemical swipes done on your bags to detect explosives. Those swipes can only detect a narrow set of explosive chemistries and everyone knows it. Some explosives notoriously popular with terror organizations can’t be detected. Everyone, including the bad guys, knows all of this.

I used to work at a place that sold a lot of fertilizers. We mostly sold stuff like Monoammonium phosphate or potassium nitrate.

One time while cleaning out a back storage room I came across an open bag of ammonium nitrate. I picked that thing up, carried it around, putting it on a cart and wheeling it around kicking up a lot of dust, all the kinds of stuff that you’d expect while cleaning out a storage room.

A day or so later I got on a plane and they swabbed me and my bag before doing so. I was startled when I didn’t raise any alarms.

I was completely under the misguided impression they something like ammonium nitrate would be detected on a person if they had handled it within a few days of being tested and that would have to explain myself.