[Spunky]

"The package was initially tested six times, and each time it came back positive for the military-grade explosive known as C4, the Coast Guard said."

This boggles the mind. Are the plastics in sprinklers made with C4 in them? Or are the recycling plastic explosive material into sprinklers?

[areafiftyone]

Either that or the tests they are doing are saying that things that really aren't explosives are testing positive. They need to get their system of testing checked out.

[Gorzaloon]

This boggles the mind. Are the plastics in sprinklers made with C4 in them? Or are the recycling plastic explosive material into sprinklers?

If they contain rubber parts such as O Rings or gaskets, the cyanuric acid antioxidants commonly used in rubbers could have given a false positive. It's a precursor to RDX. It depends on what method they were using. IR could be fooled, nitrosyl specific methods would not have been.