[Strategia_In_Ultima]

If they live in a "none" atmosphere, they'd experience no atmospheric pressure, and, although implosion probably wouldn't happen (at least with humans and similar species, we're mostly made up out of uncompressible liquids so we'd just die and spout gore), they'd experience extreme discomfort and there's a great chance that they'll die of pressure trauma. It's the opposite of what happens when you take a deep-sea fish to the surface; it's built for high environmental pressures, the pressure drops, the fish actually explodes - if you were to take a None breather to a planet with an atmosphere, the pressure would kill him. Same reason why a human shouldn't go swimming around a submarine when it's in deep water.