What is equilibrium relative humidity?

If the grain is stored in an enclosed storage environment (for example, a bag, silo, etc), the air surrounding the grain if it is well sealed is not in free contact with outside air. In this case, the relative humidity of the enclosed air will reach equilibrium with the moisture content in the grain. The final relative humidity of the enclosed air is often expressed by the ‘equilibrium relative humidity’.

The higher the grain moisture content of the stored grain, the higher the equilibrium relative humidity, and the higher the chances of mold development or loss of germination. In general, an equilibrium relative humidity inside the store of 65% or less is considered a safe prevention against the development of molds.