A desiccant is a substance that induces or sustains a state of dryness in its local area, in a moderately sealed container. It is used to trap moisture from the air, thereby maintaining humidity levels in a container. So, if you have an electrical enclosure (distribution box, breaker panel, junction box, etc.), located in a high humidity area, you may want to think about using one.
If you decide to use a desiccant, it should be placed within a closed moisture barrier or sealed container. This allows the desiccant to absorb the trapped moisture vapor inside the enclosure; therefore, it is recommended that you have well maintained gaskets on the enclosures. A Humidity Indicating Card can be placed inside the enclosure to show humidity levels and indicate when the desiccant needs to be replaced.
To determine the type and quantity of desiccant to use, you must know the type of container/enclosure you are going to place it in and calculate the volume or area of the enclosure. Select the type of desiccant to fit the application based on the amount of moisture to be absorbed, temperature, and humidity of the space. Also, make sure to check the integrity of the gaskets of your enclosure.