A desiccant sachet is considered “expired” when it has adsorbed all the moisture it can hold: at that point, it stops working.<\/p>\n\n\n\n
The speed at which it saturates does not depend on chemical degradation of the material, but on how much moisture it encounters<\/strong>.<\/p>\n\n\n\n In a well-sealed package, with little incoming moisture, the same sachet can protect the contents for months. In a permeable package, or one filled with damp materials, it can be exhausted within a few days.<\/p>\n\n\n\n You might be tempted to look for an expiration date, as on a yogurt pot. But silica gel and activated clay do not chemically degrade over time: they adsorb water vapour until they reach their maximum capacity, then they stop.<\/p>\n\n\n\n The right question, then, is not “how long does the desiccant last”, but “how much moisture will reach the desiccant, and how quickly?”<\/strong>.<\/p>\n\n\n\n The desiccant sachet always works together with the packaging. Its job is to remove the moisture contained inside the packaging and capture the moisture that penetrates from outside over time.<\/p>\n\n\n\n If the barrier material enclosing the desiccant sachet and the goods to be protected lets large amounts of moisture through, the desiccant will saturate quickly.<\/p>\n\n\n\n The key parameter is the water vapour permeability<\/strong> of the packaging material (indicated on technical datasheets as WDD or WVTR, in g\/m\u00b2 per day): the more permeable the barrier, the more moisture enters each day, the sooner the desiccant saturates.<\/p>\n\n\n\n For this reason it is essential to always use quality barrier materials, suitable for the intended purpose and for the protection duration required.<\/p>\n\n\n\n There is also the moisture that the packaging itself already contains from the start. Pallet wood, cardboard, paper fillers: they are all hygroscopic materials that hold water and release it slowly into the air inside the package.<\/p>\n\n\n\n Never place damp materials inside the packaging.<\/strong> Every gram of water contained in wood or cardboard is a gram the desiccant will have to adsorb: capacity wasted from the start.<\/p>\n\n\n\n Estimating the required amount of desiccant \u2014 and therefore the duration of protection \u2014 is not done by eye: the DIN 55474<\/strong> standard provides the calculation formula. But the formula only works if you have all the data. Here they are:<\/p>\n\n\n\n The result is the number of DIN desiccant units<\/strong> to insert in the packaging to guarantee protection for the entire time t<\/em>.<\/p>\n\n\n\n We must accept that industrial packaging always has some water vapour permeability, whether higher or lower.<\/p>\n\n\n\n If the quantity resulting from the DIN calculation is correctly applied, you have the guarantee that the packaging will be preserved for the desired duration.<\/p>\n\n\n\n DIN 55474 applies to desiccants used inside packaging. For sizing desiccants used inside shipping containers, the reference is the CTU Code: we have covered this in a dedicated article.<\/em><\/p>\n\n\n\nThe desiccant does not expire. It saturates.<\/h3>\n\n\n\n
The packaging determines the duration<\/h3>\n\n\n\n
The hidden moisture inside the packaging<\/h3>\n\n\n\n
How long it lasts, in numbers: calculation according to DIN 55474<\/h3>\n\n\n\n
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In practice<\/h3>\n\n\n\n
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