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When it comes to international shipping, moisture damage is one of the biggest risks, affecting approximately 1 in 10 shipments. Without a comprehensive moisture control strategy, products may arrive moldy, corroded, or otherwise damaged. An entire container may be rendered unusable due to unchecked humidity.
It’s clear that moisture control products are essential, but but it can be much more challenging to understand how much desiccant is enough. There’s no straightforward formula for calculating desiccant amounts. It’s a matter of understanding the factors at play and how each one contributes to damage risk.
This guide explains the different factors at play when it comes to calculating desiccant amounts, plus recommends the best products to protect your shipment.
What Are Desiccants?
Before selecting desiccants and quantities for your upcoming shipment, it’s important to understand what they are. Desiccants are hygroscopic materials, meaning they attract and absorb moisture in the atmosphere. In container shipping, they’re used to combat moisture damage throughout transit. Desiccants lower the relative humidity inside a container, absorb moisture from leaks, and ensure products arrive safely and intact.
Why How Much Desiccant You Use in Shipping Containers Matters
Each type of desiccant has a finite capacity for absorption. Depending on the type of desiccant, it may be able to absorb anywhere from 25% to 300% of its weight in moisture. Once a desiccant reaches its capacity, it’s unable to absorb any more moisture. That means, if you don’t use enough desiccant for your shipment, your products are at risk of moisture damage.
You may be wondering, why not just use way more desiccant than is necessary? Depending on the type of desiccant you use, the costs add up. Buying more desiccant than you need increases shipping costs and eats away at your profits. Instead, aim to provide just the right amount of desiccant for your container’s journey, protecting your products while still maintaining profit.
Calculating Desiccant Amount: The Variables at Play
When it comes to moisture in your shipping container, there are a number of different variables at play. Focusing on just one variable and ignoring the rest is a common and costly mistake. Instead, take the time to understand each variable, and how they all come together to affect desiccant amounts.
Container Size
First, you’ll need to consider your container size. The larger your container, the more air inside of it. Air always contains some moisture, so the more air inside your container, the more moisture. And that means a greater risk of moisture damage.
Fortunately, there’s pretty consistent guidance when it comes to calculating desiccant amounts based on container size:
Between 1 and 1.5 pounds of desiccant per 100 square feet of container space
According to this calculation, you’d need the following amounts of desiccant for these standard container sizes:
- 20-foot container: 12-18 pounds of desiccant
- 40-foot container: 24-36 pounds of desiccant
These numbers create great starting points when it comes to determining how much desiccant to use in a shipping container, but they don’t make up the whole picture.
Cargo Type
The type of cargo you’re shipping can also dramatically affect the amount of desiccant you need.
Moisture-Sensitive Cargo
Some types of products are much more sensitive to moisture than others. Electronics, pharmaceuticals, and food are all extremely moisture sensitive. Even low levels of ambient moisture can cause mold and corrosion, and permanently ruin products. For these types of shipments, you’ll need to use more desiccant.
Less Sensitive Cargo
Other types of cargo can stand up to moisture much better. Plastics and metal, for instance, are fairly insensitive to moisture. While some amount of desiccant is always required, you won’t need to use the maximum amount of desiccant for shipping containers, or the highest-absorption desiccant.
Hygroscopic Cargo
Some types of cargo can actually change moisture levels in a shipping container, too. Natural products like wood, paper, and cotton release moisture into the atmosphere. When humidity increases in your shipping container, these products will absorb the moisture. Once temperatures drop, they’ll release that moisture back into the atmosphere. If you’re shipping these types of products, you’ll want to use much more desiccant in your shipping container.
Transit Duration
Lastly, it’s important to consider your shipment’s transit duration. Much of the humidity in a shipping container is caused by fluctuations in temperature. When temperatures drop at night, the air outside your container becomes cooler than the air inside your container. The air inside your container condenses and causes moisture damage.
Here’s why that matters: The more time your shipment spends in transit, the more temperature fluctuations it will undergo. Each fluctuation is another opportunity for moisture to build inside your container. It’s important to make sure you have sufficient amounts of desiccant to protect your cargo throughout its entire journey, rather than become fully saturated when your shipment is only part way there.
Desiccant Absorption Capacity
There’s another big factor at play in determining how much desiccant to use for a shipping container: desiccant type. Different types of desiccants have wildly different absorption capacities, which are typically expressed as a percentage of the material’s weight.
On the lower end is silica gel, which only absorbs up to 40% of its weight in moisture. On the higher end is calcium chloride, which can absorb 300% of its weight. If you decide to rely on silica to protect your shipment, you’ll need 7x as much desiccant than if you were to use calcium chloride.
Discover EPGNA’s Moisture Control Solutions
At EPGNA, we offer a range of products designed to address the variables and moisture challenges outlined above. For the best possible results, use a combination of solutions.
HyBag
This hanging calcium chloride desiccant bag is designed to hang from the walls and ceiling of your shipping container and protect your cargo. It has a breathable membrane that allows moisture to travel into the bag, then locks the moisture in with a gel formula. Choose from a number of options, including the HyBag Plus+ for long journeys or sensitive cargo.
