How Moisture Affects Containers

The inside of a container has its own “climatic system”, as it is closed off from the outside world. What this means is that there can be a great variation of temperatures in them. It is not uncommon for the temperature inside a container to fluctuate between below freezing, and over 50 degrees Celsius, on one ocean voyage.

Since warm arm can hold more moisture than cold air, it becomes more humid when it cools. When cooled enough, the moisture rains out as condensation. It is this same process that causes dew and fog.

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An important aspect of moisture and condensation control is Relative Humidity. This is a percentage measure of how much moisture the air currently holds compared to how much it can hold in total. Completely dry air has a relative humidity of 0%. Generally, there is no risk of damage to cargo if the relative humidity in a container stays below 50%.

When Humidity Changes, Temperature Changes.

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Once the moisture content of the air goes beyond 100%, it rains out as condensation. This is where the problems begin, as fast changes in temperature within a container, even if it’s only of 5 degrees Celsius, can cause condensation to occur. It happens in two ways: “container rain”, where condensation occurs on the container ceiling and drips down, and “cargo sweat”, where water condenses on the cargo itself. The latter can be even more damaging.

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The problems don’t stop with condensation though. Humidity can also cause damage. At 60% humidity, metals will begin to corrode or discolour, and at over 80%, mould begins to grow. Boxes made from corrugated cardboard also begin to soften, and labels peel off. When understanding how humidity works, it is important to remember that humidity only changes as a result of changes in temperature. Air becomes more humid as it cools. A container experiences many changes in temperature as it travels, meaning the humidity in it goes up and down through a voyage. This means there is

When understanding how humidity works, it is important to remember that humidity only changes as a result of changes in temperature. Air becomes more humid as it cools. A container experiences many changes in temperature as it travels, meaning the humidity in it goes up and down through a voyage. This means there is great risk of damage. The risk for moisture damage increases when the temperature increases inside the container. This happens when it enters a warmer climate, or when it enters from outside through “container breathing”. This warm air can accept a lot more moisture, so more moisture evaporates into the warmer air when the air becomes warmer. This means when the air cools, more water is released as condensation.

The risk for moisture damage increases when the temperature increases inside the container. This happens when it enters a warmer climate, or when it enters from outside through “container breathing”. This warm air can accept a lot more moisture, so more moisture evaporates into the warmer air when the air becomes warmer. This means when the air cools, more water is released as condensation.

Temperature changes can also occur only in certain parts of a container. As air moves around inside the container, warm air can move into a colder part of the container, becoming humid and even causing condensation. This results in unusual patterns of damage, such as mould or corrosion only in certain areas of the container.

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All Absorbotec products are DMF Free, RoHS Compliant and REACH Compliant.