@JosephSible-ReinstateMonica if you don't need neutral and they're installed strictly to Code, they're "safe" in the sense that they probably won't kill you, but if you don't need neutral, you should be using NEMA 6 :P

@Shalvenay But NEMA 10 has neutral and lacks ground.

yeah, come to think of it, I might be misinterpreting 250.140...