https://www.statesman.com/news/natio...h3QmpPAXSsIRL/

That's what is stated in the article.

Congratulations! You had something with nitrates and some form of oxidiser. Been in a garden or around fertilizer recently and then used hand cream or a cheap glycerin soap by any chance? Or, more likely, was the TSA "officer" wearing gloves they'd run through their hair that contained a styling product that then touched cheap nylon baggage?

Clean gloves are important. Re-using strips is less important as the heat from each test basically cleans it each time, although proper protocol is to test/clean the strip first if you're going to re-use it. (The tests work by heating the strips very rapidly to very high temps to vapourise any nitrates or phosphates for detection and measurement.)

Explosive detection is a unique technology for both fast and precise detection and the identification of explosives traces, gunshot residuals and radioactive contrabands in a wide field of operations.

I've mentioned this before, but when my cat peed on my brand new jacket (still had tags on it), no amount of washing beforehand seemed to work. The stupid thing set off alarms at every airport during that 3 week vacation. It was very annoying and said jacket got donated when we got back home. We almost missed a connecting flight at one airport because of it so anyone with pets... well, you've been warned.

I don't know if TSA uses a different ETD system than the rest of the world but the system used by TSA is plagued with false alarms. My definition of a false alarm is when the system alerts and no contraband is found. Perhaps this is caused by operator error, reusing test swabs, improper storage of test swabs, calibration, or detection thresholds settings. In my opinion when a test system of any kind alarms, no positive reason for that alarm is identified, then the testing system is suspect and near worthless.

I would go so far as to say that TSA has never identified an actual explosive using ETD.
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The problems TSA have are manifold. 1. They don't train their testers well. 2. The testers don't adhere to the minimal and incorrectly directed training they do get. 3. TSA doesn't service their equipment properly. Or possibly at all. 4. Their testing regime is not designed to surface actual threats. Even if they were managing the mass screening via statistical risk modelling they wouldn't be using it as often as they do. It is literally no more than security theatre.

There *is* a role for trace testing. There's even a role for random trace testing - if you're that paranoid. But there is no role for random trace testing in a mass transit system other than to slow the system, and there is even less of a role when the testing is done poorly on badly maintained machines by people who don't understand what it is they're actually doing. Trace testing (like body scanners) should be used as a secondary protocol when indicated during a secondary screening.

I believe the systems are fundamentally the same but it’s possible to adjust the sensitivity, say for example between 1ppm and 100ppm- if you want to make sure you detect every single person with explosives you set it at 1ppm (or whatever the lower limit is), and throw up a bunch of false positives

when I was in Israel literally everything in my bag tested “positive”, such that it all had to be split into smaller packages, boxed and flown in a reinforced compartment on a cargo plane instead of in the belly of my plane (El Al). I’d been living on an army base at the time with my ex so I concede it’s possible there were minute traces from environmental contamination but half the stuff that came up positive had been bought in Israel

have never triggered an ETD positive before or since (touch wood) and I’m “randomly selected” literally every time I fly in Australia

Wouldn't be the first time that living with someone who deals with explosives was enough to cause a false positive.

When close to agricultural lands that have recently been set with fertilizer and subject to such dusty winds, on military bases or construction sites of sorts, it can happen.

How successful is TSA's ETD searches? Has TSA ever found an explosive item using the passenger ETD test machines? How many alarms have there been with no explosive item found?

TSA has never found an actual explosive by any means of searching. We would have known had it happened. (We know that they have missed some, however.)

TSA does not keep track of metrics such as how many pat downs it does and the outcomes of those pat downs nor does it keep track of ETD searches and the results of said searches.

P.S. Is the "blog" still in existence?

If you're referring to a website where the federal government engages in a dialogue with the people it serves, of course not.

The systems are probably based on the same technology as used in other countries and in military applications (Ion mobility spectrometry if anyone is interested; NMR is much much less sensitive) as very few other techniques can give results within seconds. Adjusting the sensitivity or at least the threshold of a 'positive' would be possible, but just as important as that is the calibration, which tells the instrument what to look for, and accuracy may drift over time if done improperly or not often enough.

The image from OP only lists 'time', which just matches something in the calibration so it's not possible to tell what it is. False positives (of similar or entirely unrelated chemicals) are possible, although the system would be designed to avoid or at least know common ones if calibrated and operated properly.

Are you speaking of glycerin, which probably causes the most false alarms?