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Quality Management

Protecting your imports from humidity

protecting imports humidity

During the past year, several of our clients encountered serious damages to their products due to humidity issues. We cover list of things which are protecting imports humidity

For example, some faced: moldy shoes, moldy car mats, unstuck carton boxes, cracked wood furniture, rusty metal (screws etc) and more. In fact there are a range of possible issues including mold, corrosion, deformation, and even functionality problems.


Despite our quality control inspection (we checked their products as per their specifications and all was okay at the time of inspection), some of these issues occurred even after previous shipments were fine.

Why is humidity sometimes an issue and sometimes not?

  • It could be raining during the loading of the container (rainy seasons in China are long) and some cartons + container floor got wet.
  • There could have been a hole in the container, allowing rain to pass on.
  • The container could have been under serious climatic conditions: heavy sun, rain, wind.
  • The products could have been damp before packing and shipment. Imagine putting a humid product inside a poly-bag with no hole ! (remember the smell of your bag after 2 weeks when you forgot to take out your football socks after a game !)
  • The packaging and packing materials were humid.

You should know that fungi, molds and mildew do not usually cause any problems below approximately 55% Relative Humidity.

So how to avoid to avoid humidity issues ?

  • Make sure your products/cartons are not loaded when it rains !
  • Make sure your products have enough time to dry up before final packing.
  • Make sure your packing and packaging (ex: outer cartons) are of good quality and not humid when placing products inside.
  • Test your product in certified laboratories: for example the ISTA 2A test entails placing the sample for 72 hours in a 38 degree Celsius, 85% humidity environment, followed by 6 hours in a 60 degree, 32% humidity environment. However, the lab testing process often is quite slow, and when time is of the essence, is may not be a possibility.

Humidity in containers:
Note that under conditions of 90% humidity and 30 degrees, 1 cubic meter of air contains nearly 30g of water…
Studies show that a container can have its temperature vary from from -4ºF to 158ºF (-20º to 70ºCelsius), more usually between 32ºF to 122ºF (0º to 50º Celsius), while the relative Humidity Measurement range is 5% to 95% !! See those very interesting articles (here and here and also here) about temperature and humidity variations inside a container.
See here a graph showing the variation of temperature in a normal brown container OVER 1 DAY:

Fundamentally there are two different kinds of condensation : cargo sweat and container sweat. Cargo sweat occurs when moving cargo (carton or container) from a cold or temperate climate to a tropical one. The air containing moisture or water vapor condenses on the cargo or its packing. Container sweat occurs when water vapor in the air condensing or forming on the inside surfaces of the container when moving from tropical or temperate climates to cooler areas.

So how to avoid humidity in containers when importing?
You can have high quality desiccants absorbing humidity inside your cargos, ie: inside your container and inside your cartons !

It is important to put the right needed quantity of desiccants but also to select desiccants that work for a good amount of time. Actually, if you are to purchase cheap dessicants, they will start releasing humidity back into the air once they are full, so it is important to get ones of good quality. A good dessicant will last 45 days, whereas a basic silica gel pack will only last 48 hours… FYI, sand is a natural desiccant, like rice also (have you never put rice in a salt shaker?).

One of our partners Superdry is a supplier of high quality desiccants (made of calcium chloride/ supposed to be the best among a long list) and they recommend using 4x 1kg packets for every 20 foot container (remember to seal your container with tape or you will start absorbing the humidity from the air outside the container !) + placing desiccants inside cartons if the products are humidity sensitive (cartons/textile/food etc).


AQF Operations team

Our team consists of supervisors specialized in various types of products. We handle client requests, analyse their instructions & specifications to provide qualitative inspection protocols to the inspectors for high quality reports. With the Quality Control Blog we want to tell stories taken from our daily activity to help the importers in sourcing better and safer. Get to know us!

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4 responses to “Protecting your imports from humidity”

  1. nicholas says:

    I know this is an old blog but i hve a question. I import furnitures and reicived several sofas with mildew (enough that it has stained the leather and color/sealer). There was no silica bags in the wraped sofas. The rest of container seems to be fine because they had severals silica bags. What ressources is there to force the fabricator to reimburse sofas and shipping?

  2. David Fisher says:

    Indeed so! Unfortunately, many people just starting to import are the ones hit hardest with this, as it often isn’t even considered.

  3. This takes some serious control over sourcing to prevent humidity issues. Enough to make any person lose a little sleep!


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