Depending on what you are storing, moisture can be a concern. Excess humidity in the air can damage your books, clothing, electronics, and tools as well as encourage the growth of mold and mildew. Cleaning and drying wet or damp items before placing them in storage helps reduce additional moisture in the air. But your local climate may be moist during the winter or rainy season, naturally adding to the humidity in your storage unit.
There are many commercial moisture-absorbing products sold at home centers and storage facilities. These products may contain activated alumina, calcium chloride, potassium chloride, silica gel, sodium chloride or a combination of ingredients intended to absorb excess moisture or humidity from the air. These products may be toxic; keep them out of reach of children and pets.
There is a good reason why manufacturers warn you to keep your charcoal briquettes in a dry location; they absorb water from the air. By placing a bucket of plain, inexpensive briquettes in your storage unit, you can reduce the humidity. You should replace the briquettes every 30 to 60 days to keep the air fresh and dry.
You may already use clay kitty litter to soak up oil spills in your garage. It works equally well to absorb the humidity in a storage facility. Simply tear open a bag or open a bucket of kitty litter and place it in the middle of the building. The clay will absorb the moisture in the air, keeping your possessions safe from mold and mildew.
When electricity is available, a dehumidifier helps to reduce moisture in the air in your storage building. Unlike passive moisture-absorbing methods, however, you can use a dehumidifier only when the temperature is above 70 degrees Fahrenheit. In an unheated storage building, it may not be practical for use in winter. In addition, you’ll have to empty the water tank regularly unless you can attach it to a floor drain.
Used along with the passive methods of reducing moisture in a storage building, a box fan or oscillating fan can help keep the humidity level low. Good air circulation keeps the air dry and prevents mold and mildew from forming on the storage boxes and walls.