Jason shakes his head. "Not a gas. It's... it's something that certain metals do. Like how fire gives off heat, only you can't feel it. There's no... sensory indication it's there, not unless it's really bad and then usually you taste something... vaguely metallic. But other than that, you'll never know it's there unless you've got a machine that detects it, or you suddenly start getting sick. I'll agree about it being a pain, though."