This article contains some observations that may be of interest to readers of this board.
...The x-ray machines used in the PreCheck checkpoints are different from those used in the non-PreCheck checkpoints. The TSA tester said he could not tell me what the differences were, other than that they were “optimized for different things,” or something to that effect....
...The Sikh representatives wanted to know why TSA agents always demand to search their turbans even when they are cleared by the body scanners (AKA Advanced Imaging Technology or “AIT” machines). Some of the Sikhs asked to go through the AITs, and we all saw that the machine gave them the “all clear” with no alarm or “anomaly” being indicated at their turbans. The basic answer was, as one of the testers explained, that “there are vulnerabilities on the AIT.”
...With an older model of the EDTs, she said, the agency realized that they were even alarming on the gloves that the TSA screeners wear on their hands, which were discovered to contain nitrates. The screener said that when the alarm rate rose this winter, it was also discovered that some commonly deployed varieties of road salt triggered the machine. Even if the swab is left out in the open too long, she said, it can generate a false alarm just from soaking up background nitrates from the air....