ALEX CHADWICK, host:
The plots we have been hearing about have involved liquid explosives reportedly at the center of all this. And to learn more about how terrorists might use these kinds of things, we have NPR science correspondent David Kestenbaum with us now. David, what kinds of liquids do security officials look for?
DAVID KESTENBAUM reporting:
Among other things, they'd have to worry about the sort of bottles you might find under your sink. I talked to Chris Ronay(ph), who is former chief of explosives at the FBI, and he used to teach this class for investigators and he said he would stand up in front of the class with chemicals taken literally from other the sink and mix them together and set some of them off. And his point was that if an agent is searching a house where they think a bomber is, you know, you need to look for all kinds of things. There's not anything terribly special about a liquid explosive versus a solid explosive. Ronay said he could think of one company that used to make liquid explosives for commercial use, but he thinks it went out of business.
CHADWICK: Don't these things have - at least bleach and other things under my kitchen sink, they have pretty distinctive odors. They'd be quite noticeable, I would think, if you were trying to get them on board a plane.
KESTENBAUM: They do if you're smelling them, and the airports have these doorways, you know, that you walk through with the sniffers that puff at you and they will take swabs of your bags sometimes. Those are looking mostly for residues from solid explosives. So if you have something that's in a liquid in a bottle, you know, it could be harder, harder to detect. Experts say you need good detectors and you also need good people running them. So if you get a positive signal, someone needs to be able to say that's not the shampoo bottle, that's something else.
CHADWICK: And these are really explosives. We're not talking about flammables, we're talking about something that would actually blow up and maybe blow up enough to explode a plane.
KESTENBAUM: Right, and as Rob Gifford mentioned the concern is that they may be easier to smuggle. So you have one person bring on liquid A, chemical A. Someone else brings on chemical B, and on their own they're sort of innocuous, but then in the bathroom someone mixes them together and you have an explosive. You don't necessarily need a fancy detonator. Nitroglycerin, that's the explosive you probably remember from old movies. People would pour it into a safe and blow it up. Alfred Nobel, when he was working with that, blew up a factory and killed his brother. That's why sticks of TNT were such an advantage. You could throw them against the wall and they - they wouldn't blow up.
CHADWICK: NPR science correspondent David Kestenbaum, David, thank you.
KESTENBAUM: You're welcome.
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