I was thinking about a hat or shoes worn at a shooting range...that might test positive at TSA inspection too?
Usually the sensors t the gates are scanning for external residue- or for radiation. I’ve carried cans of smokeless powder through the gates w/ no ill effects, but a few sacks of lawn fertilizer pinged.
I shoot a lot, and often came through the gate with bags of fired brass in the cabin, no issues.
Had a nuke stress test off post, had a note from the docs office in case I set off the rad detectors, supposedly technicium can set off the detector. I didn’t so I didn’t tell the DA police either....
Standoff detection is a science & technology that still has a ways to go. Worked on a research project where lasers and a telescope linked to a spectrometer could detect ammonium nitrate in bulk at 300 m, trace amounts at 20 m. But you had to scan specific areas of a surface- it was not an “area” detector. The computer controlling it would shoot 30 pulses a second in a raster pattern on door handles, etc to excite the molecules and emit or fluoresce so the spec could “see” the residue and decide what it was. Algorithm city. Then we pulled out of IRQ and funding dried up.