Originally Posted by
Boggie Dog
If a testing device alerts often enough and no item is found to cause the alert then the operator will soon give less attention to the results.
Of course. Just watch the screeners, not just TSA, but ANY screeners, run the swab tests. They have zero expectation of finding any explosives. While the poor passenger hovers about nervously wondering if today it's his turn for a machine/operator screw-up and whatever humiliation accompanies that. All this for a test that produces 100% bad results.