What was the security guy looking for?

I recently flew on some business trips and I noticed something new that the security guys are doing (or at least new since my last business trip 1.5 years ago).

They have this wand/stick into which they place a small square of some type of white cloth and if you have a laptop computer, they rub the cloth over the case of the laptop, and then open up the laptop and run it over the screen and keyboard.
Then they take the cloth and put it into a machine for some kind of analysis.

What are they looking for? (The airport security guys don’t seem to like to answer such questions :slight_smile: ). Okay obviously they are looking for bombs or some kind of instrument of terrorism, but what specifically are they looking for. I’m very curious!

The wand is to detect explosives residue.

Explosives Residue. The cloth is designed to pick up any residue that would be on the laptop had you taken out the innards and made it into a bomb, the machine will then alert them to this should it be the case. I have heard of them swabbing people’s hands as well as laptops and other hand luggage. Bear in mind the relatively tiny amount of explosive that would be required to take a plane out of the air, and wonder why this wasn’t done before 9/11.

Ahhh, FBG got there first, preview is my friend.

I’m pretty sure it was. The few times I’ve travelled with my laptop it always got swabbed, only they swabbed around the zippers and the handles of the laptop bag without actually opening the bag.

I recall, back before 9/11, having to turn on my pager to demonstrate that it was a working pager and not just a plastic shell filled with explosives. I guess this was a more primitive version of the same test, but they were definitely doing some sort of check of this type pre-9/11.

If you’ve been trap-shooting or hunting recently, will the powder residue on your shoes freak out the airport security guys?

Hard to say, but I really doubt it. I can say I’ve gone target shooting handguns the day before a trip and possibly had powder residue still on my skin, and never had a problem when they swabbed the laptop bag. I worried about it at the time which is why I remember.

IIRC there is an urban legend that eating too many Polish sausages at the airport hot dog stands will set it off, due to the high levels of “nitrates” in the meat.

Also, swabbing was done, rarely, at some airports prior to 9/11.

I’m not sure, but I think gunpowder residue and the sort of explosive residue they’re looking for with the swabs at the airport are chemically different.

That aside, I understand it IS possible to detect gun residues for some time after firing a weapon.

Yeah, I’m not sure why’d they want to look for gunpowder residue. Wouldn’t you basically need some sort of plastic explosive to do enough damage with a small amount of material?

Yep, I’d had it done to my backpack several times prior to the newer security measures being in place; usually when travelling with my now-husband (we’re a pretty scruffy looking couple on vacation, I guess). With the new measures, he’s the one always checked now and I’ve never been pulled aside while travelling with him since.

Although except for Reid (shoe guy), this wouldn’t have stopped 9/11, I think.

The only time recently where my checked bags were searched by TSA was after I was visiting my folks in Idaho and spent part of a day black powder shooting. I had the unwashed shirt from that day (which had a lot of black powder residue on it) in my bag. I’m not sure if that’s why the bag was searched, but there may be a correlation. There were no problems going through security, though.


I had to turn on my boombox when flying from Florida to Detroit, but not going the other way. I assumed they were looking for drugs, not explosives. This was 1989.


I should have been able to guess that! What threw me off is that they didn’t seem to be checking anything else with the wand … not my hands, or laptop bag, or anything in my purse, or my knapsack (with the exception of the x-ray device that checks all my carry-on including my laptop)

Does anyone know how the machine works? Are they looking at some sort of spectroscopic data (like IR), GC-MS (I doubt this), or do they have some chemical that only binds to explosive residues?


reconstruct the circumstances of the incident: how far away was the gun fired? was it a suicide or murder? who fired the shot?

4. Beyond 3 feet there will be now deposits except the bullet wipe of the bullets passage around the hole.
color contrast is such that reside is not observed on the cloth - here infrared light and photography can reveal the presence of these deposits

Heraeus Noblelight GmbH’s Fiber-Light miniature UV light source is a deuterium lamp that satisfies the requirements for UV spectroscopy in situ. Small UV spectroscopy instruments equipped with the light source, and small spectrometer and numerical evaluation techniques now allow on-site continuous water analysis for nitrates, nitrides, bisulphides or total nitrogen and phosphorous. The high-frequency-excited lamp, which is designed to provide suitable UV intensity and stability under harsh environmental conditions, provides more than 1000 h of operation and requires approximately 3 W.

Somewhat related: I recently flew through the Kansas City Airport, which by far had the most thorough security I’ve ever seen. All the restaurants, shops, and restrooms are outside of security. They did this ‘swab test’ of my CD player, and then (since I got singled out for extra-special screening, randomly), they also ran chemical-sensitive paper over your shoes and ankles.

A few months ago I had my checked baggage get the wand treatment before boarding an international flight. One of my bags came back positive. Turns out I had left a small box of wooden matches in one of my travel bags from a recent camping trip.

While waiting for them to figure out what had triggered it, the security guy mentioned that some types of food would set it off.

He just handed me the box of matches and said I could put them in my carry-on instead. I threw them away before boarding, but after going through the security checkpoint.