Right-wing Conspiracy Theories
The level of detail of the news story is too low to make an informed judgement, but I have an idea of what may have happened - and of why innocuous items may result positive for explosives.
The sensors used for field tests are simple devices (often, a sort of mass spectrometer called ion mobility spectrometer) compared to laboratory analytical instruments, built to detect one class of compounds - in this case, explosives. What most explosives (TNT, RDX, HMX) have in common is the presence of nitro groups, which I expect to be the main feature of the IMS signature of explosives. However, nitro groups are also contained in other molecules: dyes, certain solvents and drugs. It is also conceivable that compounds like amines, amides and urethanes (that is, common plastics) may give IMS signatures similar to explosives. Also fertilizers contain high amounts of nitrogen, often as nitrates an ureas (which are not nitro groups, but somewhat close). I'm available to conduct an experimental campaign to clarify these issues, if I can find a sponsor...
There is also the selectivity problem: high selectivity is already difficult to achieve with laboratory instuments; field instruments cannot go very far. This means that they aren't very good at discriminating between different chemicals especially within the same class.
As a matter of design bias, I'd prefer my explosive detector to give more false positives than false negatives, because a false positive is a pain in the back, but a false negative can cost many lives.
The story says that the suspect package in fact contained "sprinkler parts", which is another exercise in vagueness. But if these sprinklers became contaminated with some chemical - in the case of agricultural sprinklers, fertilizers - they may result positive for explosives. An investigation should be launched anyway, at least to find who caused that mess by leaving a suspicious package around.
But instead of acting rationally and fact-checking, a lot of LGFers don the tinfoil hat:
Prysorra 1/8/2007 05:46PM PST
*I answer my own question...
a. False positive for political pressure
b. Security coverup for political reason.
c. They misread their instruments.
C is not likely.
BabbaZee 1/9/2007 05:36AM PSTAnd yes, these are only two comments out of 260+, but most of the few on-topic comments have a similar tone. Only a handful of commenters tried to understand what may have actually happened, and apparently none even did a quick search for the principles of explosive detection.
I seriously doubt they will EVER tell us the truth on these matters until something actually detonates. Everything that is stopped in time will be reported as "false alarms"
Whenever a false alarm occurs, at LGF it's always like this - many don't even admit the existence of false alarms; there must always be evil, scheming jihadis somewhere and governmental cover-ups to keep the sheeple blissfully unaware. Sounds familiar? It should; it's the same basis of all conspiracy theories. Change a few words, and you'll get Loose Change 911. (Sligthly edited on 10/01)