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Units of mg/Nm3 for gas concentrations

  1. Nov 12, 2004 #1
    Hi all,

    Sometimes I come across the units of mg/Nm3 for gas concentrations. What I would like to ask is why we need to specify that we are talking about mg per Normal cubic meter? Why not just mg per cubic meter? Whatś that Normal for?

    Thanks in advance.

  2. jcsd
  3. Nov 13, 2004 #2


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    The volume occupied by a gas is a function of the pressure and temperature. So that, you have to refer it to a standard conditions (i.e. atmospheric or normal conditions).

    EDIT: Those engineers that have designed pneumatic systems know that very well, because volume rates of air are always referred to these normal conditions.
    Last edited: Nov 13, 2004
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