Desiccants adsorb water vapour and reduce relative humidity inside an enclosed pack. In controlled export packaging, they are commonly used together with a moisture barrier bag and a humidity indicator card to verify that the pack stayed dry.
When do you need desiccants?
Use desiccants when one or more of these are true:
- Sea freight or strong temperature cycling
High condensation risk and “container rain” exposure make humidity control critical. - Long-term storage or unknown delays
The longer the dwell time, the higher the probability of a high-humidity event. - You cannot guarantee that parts are fully dry at sealing
If moisture is sealed in, desiccant stabilises the microclimate. - Large void volume inside the package
More air volume means more water vapour capacity, so humidity can rise quickly. - High value surfaces and low defect tolerance
If even light corrosion results in rework, claims, or rejection, desiccant is justified as a risk control.
When can you often skip desiccants?
You can often skip desiccants if all of the following are true:
- Short transport and stable conditions (domestic routes, quick unpacking)
- VCI packaging is used correctly, and the enclosure remains adequately sealed
- The pack is dry after sealing, and the sealing quality is consistent
- You have evidence, for example, humidity indicator cards or internal shipment data, showing that the in-pack humidity stays within your target range
The most common cause of rust is not “no desiccant”. It is packing wet parts or using desiccant without a true moisture barrier, which allows ambient humidity to continuously leak in.