Why do airports sometimes detect traces of explosives in bags?
So there's a (usually spot check) inspection point at airports sometimes, and they do a check for traces of explosives/gunpowder residue.
I've never had any problems, but a couple of friends have had it go off innocently - where they've actually detected something, and searched their bags.
Once this was warranted - turned out his father had cleaned his shotgun over his bag, but the other has no idea how there could possible be anything.
How does this happen? Is it faulty equipment, or what?
Best Answer
The usual problem is a reaction on a generic "explosive"--which falsely reacts to glycerin. You'll find glycerin in a lot of skin products.
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Can airport security detect bombs?
Backscatter passenger scanners are used to detect threats such as weapons or explosives that a person could be carrying under their clothing. Backscatter machines use very low energy x-rays that are reflected back to the machine itself.How do airports test for explosives?
The airport official swabs the outside of your hand luggage liberally, before inserting the swab into a mysterious machine. This process, known officially as explosive trace detection, is doing just that\u2014checking to see if your luggage has come into contact with a bomb or explosive material.How does explosive detection system work?
Trace detection involves the chemical detection of explosives by collecting and analysing tiny amounts of explosive vapour or particles (a microscopic amount of explosives) [4] and looking for residue or contamination from handling or being in proximity to explosive materials.What do they swab for at airport security?
Explosive Trace Detection (Swabbing) Screening officers may swab your carry-on baggage, clothing, shoes or laptop. When a trace of person is required, the screening officer will swab your hands, waist area and foot (or footwear) and then use ETD technology to test for explosives.The Science of Airport Security
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Answer 2
It might be what you have described but it also might be a simple matter of where the bag had been but basically a false positive.
For example if you visit agricultural areas you might come in contact with Ammonium Nitrate (the stuff that blew up in West, Texas), which is a common fertilizer but also can be used to make gunpowder or other type of explosive materials. So that might be what is being chemically detected by the "sniffers" or using swabs. Additionally ammonium nitrate is derived from common ammonia (found in a lot of household cleaners), which if present in significant quantity could be construed as precursor for explosives.
There is also a great presentation from University of Wisconsin on what could be detected by the chemical methods, which basically expands the list of all matters of Nitrogen based compounds.
Answer 3
If I had to guess, the equipment for detecting the chemicals has to be very sensitive so that it detects the faintest traces of it (to err on the side of caution). False positives are a hassle, but a false negative could have disastrous consequences.
Very sensitive equipment has to have a ton of gain to detect small signal levels. With a ton of gain comes a lot of noise. Separating signal from noise is a delicate business.
Then there is the problem that chemical compounds occur in vast combinations. The equipment has to identify some known explosives, from among billions of harmless molecules. It has to do this without actually reconstructing the molecular shape, which would require something like X-ray crystallography. It has to also work without having a sizeable sample of the substance which would be needed for Infra-Red or mass spectroscopy; just a whiff from a suitcase.
It's pretty amazing that this stuff works at all, really. It's amazing what a human, or for that matter, canine nose is capable of, too.
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