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Moisture Damage


Relative Humidity and Moisture Damage

Mold and condensation problems occur when the relative humidity is too high. Relative humidity is the amount of water vapor in the air compared to the amount the air can hold. Warm air can hold more moisture than cold air. So, if warm air and cold air contain the same amount of moisture, the warm air will have a lower relative humidity.

Two conditions cause the relative humidity to rise: when the temperature falls or when moisture is added to the air. Cold surfaces, such as windows or the inside of an exterior wall, create localized cold spots which reduce the amount of moisture the air can hold and raise its relative humidity. When water vapor is produced but is not being removed from the container, this, too, will raise the relative humidity.

Most molds grow at relative humidities of 70% or higher. Mold and mildew are virtually always present. They are not picky eaters and can find a feast in any shipping containers. Many building materials (from wood to plastic foam) provide nutrients for molds. When nutrients are combined with adequate moisture, molds can thrive.


How does Moisture Form within Shipping Containers?

Humidity from Loading Location

If your goods are loaded in a tropical location, such as Australia or Hong Kong, the increased moisture in the air will be held within the container creating condensation as the freight moves through different climates. This humidity can also increase the amount of water held by packing materials and dunnage.

Temperature Changes En Route

In addition to colder temperatures releasing moisture in the air from the loading location, changes in temperate during your supply chain can also result in water damaged goods. These temperature changes could also be caused by an unexpected cold front or even just the drop in temperature that comes with the transition from day to night.

As weather conditions fluctuate, the colder air is not able to hold the moisture accumulated during higher temperatures. As the moisture is released, condensation forms within the container resulting in container rain.


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