[berberous]

I don't know enough about how these things work to verify his comment that metal is only a concern if you dry hit, but a dry hit just means it ran out of juice and you didn't notice, so you accidentally inhale a disgusting taste of burnt metal/fabric, rather than vaporized liquid. Normally though, you have liquid sitting in a tank touching metal, glass and/or plastic. Maybe glass and good metals don't leach into the liquid, but there are tons of cheaply made devices out there, and I wouldn't bet my health without seeing better studies that some sort of metallic or plastic compounds couldn't leach into the liquid, to then be vaporized and inhaled.