Originally Posted by Bart
Am I oversimplifying here? I don't know. I do know that these same machines can be recalibrated to detect all sorts of drugs by changing the definitions algorithms. We do not use them as drug-detection machines, but they can certainly be used in that capacity. What these machines do is alert on whatever you define for them to alert on; hence, my confusion about why the call for "liquid explosive detectors" when it's just a simple matter of recalibrating the machine.
No, you're not really oversimplifying. The ETD machines in use are, as far as I know, all based on gas chromatagraph - mass spectrometer technology. It should just be a software update to add additional substances to alarm upon. I'm not 100% sure how the airport-based machines work, having only used big and lumbering lab-based GC/MS machines, but the principles should be very similar.
The bigger question is how existing ETD machines could be better used. Swab everyone / every bag? That's unfortunately not going to work, even if we add more ETD machines. The puffers were supposed to address this issue, being essentially giant GC/MS machines that use their puffs of air to dislodge traces to analyze, but they've never exactly been perfect technology. Handheld "sniffers" might work better--just incorporate them into the carry-on x-ray scan and have a few for screeners to carry around for secondaries / closer looks at stuff. However, I'm also not sure how well-developed such "sniffer" technology is just yet.
I have advocated that if we're going to have a liquids ban, then to encourage checking of 8 oz or more of liquids and require ETD swabs of any others, in a separate line (if a liquid is seen, send the person to that line). Of course, seeing a liquid is another issue entirely... and not one the x-ray operators are well-prepared for yet.
ETD is the best line of defense
at the checkpoint against explosives... but to make it effective, we're going to have to look at how it's used.