I wonder how the THC thing could possibly work. I opt out at every checkpoint, and each time, they maximize body contact and then generate an input to those machines. Wouldn't it go off for anyone who had smoked up earlier in the day, or the preceding day? It seems like they'd be spending all their time doing drug searches.
(Don't get me wrong: drug searches at TSA checkpoints are extremely alarming, because TSA has been given a near all-access pass to mechanically searching people).
Fun fact: if you do any welding before you get on a flight, there's a good chance you'll set those things off.
I've literally spent a night putting on a fireworks show, gotten up and flown the next day, and not set off the alarm. I've also at a different time been completely clean, set off the alarm for gunpowder (I could see the screen), and then had the TSA wave me through.
They don't know, they don't care, they don't do anything. Their sole purpose is to make people more comfortable with invasive government overreach.
Similar experience here. I was at a party the evening before a flight and had loads of rockets and small mortars stuffed in my cargo shorts, which we were running around and shooting at each other (alcohol may have been involved).
Next morning at the airport was my first time seeing these machines. As the machines doors opened and closed, jets of air puffing at the passengers ahead of me, I wondered about the shorts which I still had on. I looked down at the empty pockets and they were literally sparkling with gunpowder and other residue from the fireworks the night before. 'Let's see what happens' was my only thought and I felt a bit let down when I got through with no problem.
Edit: Shorts sparkling in the light with some kind of crystalline residue from the fireworks, not sparkling like a lit sparkler, which would have been even more impressive.
I most recently triggered it at SFO after wearing clothing I had gone go carting in the day before. First time for me. The enhanced screening was fun. Aside, SFO security is a contractor, not TSA.
(Don't get me wrong: drug searches at TSA checkpoints are extremely alarming, because TSA has been given a near all-access pass to mechanically searching people).
Fun fact: if you do any welding before you get on a flight, there's a good chance you'll set those things off.