Moisture damage in container transport occurs due to the fact that warm air holds more moisture than the cold air. However moisture damage happens even where there is no condensation. As many grades of steel will start to corrode at a relative humidity of about 70%. Mold growth could begin after even a short period over 80%. .Moisture can get into the air in the container from the outside or by evaporation from the cargo. When the temperature in the container changes or there is a difference in temperature between different parts of the cargo.