Well... maybe my question is a stupid one, but what is the matter with metal pipes? From what i know, most metals (except tin, and maybe lead) has a melting point greater than the temperatures reached inside a pipe, and a boiling point FAR greater. So, inhaling metal vapours would be impossible, and i think no one would inhale molten metal... then what is the matter with it? Could someone explain me please?

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"Everything we do, everything we are, rests on our personal power. If we have enough of it, one word uttered to us might be sufficient to change the course of our lives. But if we don't have enough personal power, the most magnificent piece of wisdom can be revealed to us and that revelation won't make a damn bit of difference." Don Juan Matus - Tales of Power