Originally Posted by
FlyerGoldII
Last couple of times, I have passed the metal detector machine (in the TSA precheck lane), and the alarm had gone off.
I thought it meant I required secondary screening, but it was really for ETD screening - ie my hands were swabbed and the swab was put in the ETC machine.
The metal detector has two beeps - the normal one indicating the presence of (too much) metal, and a long beep, which is a "random" alarm that indicates you have been selected for additional screening.
In the past, additional screening in PreCheck meant you would get a hand swab. Now, the procedure has changed somewhat. TSA has installed MMW scanners in PreCheck lanes in many airports - the most recent TSA documentation says that there are 68 airports with MMW scanners installed in the PreCheck lanes.
If you are "randomly" selected for additional screening at an airport with MMW scanners installed in PreCheck, you will be steered to the scanner. In airports without MMW scanners installed in PreCheck, you will get the hand swab.
Is the chance of such screening for a TSA precheck passenger similar or lower than a nonTSA precheck passenger?
It depends. The frequency of "random" selections can be controlled by TSA, so there may be times when there are very few "random" selections for additional screening, or there may be times when nearly everyone is "randomly" selected, and everything in between.
As a result, it's getting much more difficult to have a feel for how long security screening is going to take in PreCheck lines. My rule of thumb is that anytime there's a newsworthy terrorist/security incident (such as the one at MSY two days ago), it's prudent to assume there will be a higher frequency of "random" alarms for a week or so afterward, so there will be a better chance of getting selected for additional screening.
If you're fortunate enough to be entering an airport without MMW scanners in the PreCheck lanes, it shouldn't slow you down too much. If you're entering an airport with MMW scanners in PreCheck, plan for additional time. Going through the scanner is significantly slower than a hand swab, and if you end up needing manual resolution (i.e. a post-scanner grope), or if you decide to opt out of the scanner, it will take much longer IME.