Explosive Trace Detection
 

Can anybody interpret this ETD result:

I can't interpret but from my observation of TSA ETD practices at DFW yesterday I would suspect the validity of these tests. My bag was pulled for extra screening, the culprit was a ziplock with some candy and cheese crackers. The screener took a used ETD swab and sampled the ziplock bag all while wearing gloves that were potentially already contaminated. I observed the exact same process by a different screener checking a ladies toaster snacks except he tested each wrapped package.

I would at a minimum require the screener to test their gloves for contamination before testing a travelers property and I question reusing test swabs at all.

Edit to add: Just a side note, all the concern over a bag of candy while my CPAP didn't get a seconds notice and my Kippy bag never came out of my bag.

IF you have the presence of mind to do so, you should always require clean gloves and a clean swab before testing anything. Not always easy to do in the face of mass confusion at a checkpoint however.

If anything it shows that the TSA might want to upgrade its printers. This looks like a dot matrix printout from 1985.

Yes, it means someone used hand lotion.

That will be $211,235,386.26 please, TSA. TIA.

Well, when a person is gobsmacked at TSA idiocy some things slip by.

Looks a little like NMR (Nuclear Magnetic Resonance) where you get visible peaks at certain values on a spectrum of spin states.
Those peaks might correspond to nitrates, which are common in explosives. Also in food preservatives.
Given that only around 1 set of luggage in 50 million is packed with explosives I think the whole charade is mostly for psychological effect.

https://pjmedia.com/instapundit/305180/

Sigh......grrrrrrr......

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Wonder how long it will take before the TSA Blog lists the miss like they do the finds?

TSA officer at Texas airport missed loaded gun, according to police reports

Interesting, and admirable, reaction by the passenger. If that were to happen to me (I own no firearms), I casually leave the secure area and deal with it elsewhere.

If for some reason my firearm makes it to the TSA line without my knowledge I will consider it a supreme act of self stupidity, beg for mercy and consider the lost firearm a stupid tax. Any resolution that does not include a huge fine or jail time would be more than I deserve.

I don't know why people feel the need to self-incriminate when they make it through a TSA checkpoint with something? The simplest thing would have been for the guy to leave the secure area, go back to his car, hide the gun somewhere inside, and go through security again. Now, he runs the risk of a punitive TSA administrative fine. But, the good news is that it got a TSA clerk fired.

It was interesting that they fired the clerk instantly while sexual assaulters go unpunished. I guess he got fired for embarrassing the TSA.

The screener is a government employee with union representation. Unless this person was in a probation period I wouldn't be to confident they stay fired.

Do we know he was fired instantly? This incident happened in June and we are just now learning of it.

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?

I wasn't specifically talking about any chemical - without the manual and/or calibration for it there's no way to know what it looks for and how.

Or nitrates?