Tom, it can alarm on all those items. It will detect those items, and that does not mean it has alarmed. There is a threshold. ETDs, if they alarmed on every "hit", would shut the checkpoint down. Everyone test would alarm.

Sometimes, yes. However, having worked in places where a significant amount of those shoes I have test have been through such fields, and not having that many alarms, I can state that you have inadvertently over-stated how often such alarms will happen.

I would guess that exposure to commercial fertilizers such as at the golf course or on farms would be more likely to generate an alarm than those sold for home use. In general, home use fertilizers are encapsulated for slow release. With commercial applications it is often the case that the application is for an immediate need.

I am not trying to be rude, but its much more involved than: ETD detect a specific chemical, thus, ETD alarm. If that were the case, almost every ETD test we run would alarm. It was surprising to me when I started working with ETDs just how much they detect, I had no idea we all had those chemicals on us and on our property. But in retrospect its not surprising.

But to specifically address what you stated, the slow release vs immediate release, really wouldn't matter.

Tell that to my colleague who showed up in Atlanta for a corporate leadership meeting with no shoes. They were confiscated - yes, confiscated - by a fellow employee of your organization in the midwest.

The problem is not the "not many alarms", it's that there is no way of knowing whether an alarm will happen, and the consequences of such an alarm range from a full "resolution" search, to confiscation of shoes, to not not flying that day (and possible referral to law enforcement).

Given that, there is no such thing as "overstatement" any more than the TSA believes that the terrorist threat on any give flight is overstated.

Why is there a "threshold" on glycerine and fertilizer if the units can apparently detect less than threshold amounts of actual explosives?

You assume a lot, Tom. And you assume incorrectly. I am not sure if you understand how ETDs work.

I don't understand your question. There has to be a "threshold" on every chemical detected or almost everybody would alarm.

Then please explain.

According to SATTSO, the units can detect very small amounts of explosives. Such small amounts that the TSA has decided that even when these small traces of actual explosives are detected, the levels don't meet an alarm threshold. Why then have any alarm threshold for non-explosives such as glycerine?

If the TSA is worried about masking, then the detection of small traces of explosives should alarm.

If there are actual explosives, then in addition to these other items, such as glycerine, there would be actual explosives the machines would detect.

Wow. Tom, you have just confirmed to me you have absolutely no idea what your are talking about concerning this matter.

I wouldn't be surprised if a decision was made to keep using this unreliable technology for the sole purpose of meeting secondary search quotas. It's much easier to explain that a search has been necessitated by an "alarm" detecting the presence of explosives than it is to explain that ~somebody~ (or a bunch of bodies) every single day has to get searched just because and today is your lucky day! Less arguments from passengers if it can be blamed on an "alarm".

You are more than welcome to explain what I got wrong and why.

All of the talk about what is and what is not detected, and about thresholds that alarm is mooted by the results of this activity. Nearly 100% bad results in which innocent people are getting bum rushed to the private hut to have their sex organs massaged thoroughly. If I'm going to the airport on legitimate business, and have done nothing illegal, and have followed the TSA rules in not bringing forbidden items, then I have full reason to expect that these clowns will LEAVE ME THE F**K ALONE. If you people can't meet this really low baseline of expectation, then you should not be performing this function.

^ +100,000 Well put, nachtnebel!

Edit to add: God, I wish I had said that!