Describes procedures for determining the equilibrium relative humidity of paper and paperboard. Paper which is dimensionally stable at a particular relative humidity and temperature will remain unchanged as long as this condition is maintained. Printers and paper converters can maintain a particular humidity and temperature condition more easily than they can regulate the moisture content of the paper to adjust for a change in its environment. Hence, for many purposes equilibrium relative humidity at a specified temperature is more significant than the moisture content of the paper.