FedEx refuses shipment of made-up stuff, empty cans

Quote from here:

FedEx guy: Nope. You can't ship these either.
Me: But... they're empty! It's just air. And... nitrogen? It's, like,
almost 80% of the atmosphere. There's nothing dangerous about nitrogen, even if
it were pure.
FedEx guy: They look too much like bomb-making materials.
Me [going into dumbfounded mode]: Bomb... Neon? What? Is there anything
here I can legally ship? How about this bottle of tap water?

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