A true story of security theatre from FedEx, refusing to transport empty containers not because of what's in them (sugar and air) but because of how they're labelled.
The FedEx guy then grabs cans of nitrogen (N2) and neon (Ne), with their store-advertised "purity" of 78.084% and 0.0018% respectively (which was our way of being clever about selling cans of normal air, since that's their percentage in the atmosphere [...]
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.