Avoid using cardboard boxes for basement storage.
HealthyHouseTM CleanAir Tip
Cardboard is a very porous material that is primarily composed of cellulose. Cardboard is also absorptive and tends to attract moisture. Both of these properties, make cardboard an ideal medium for mold growth.
The majority of basement walls and floors are built with poured concrete. Concrete has a remarkable ability to draw moisture through it. This property is called capillary action. Concrete can drawn water up vertically through it to a theoretical height of 6 miles counteracting the force of gravity. Basements often have elevated humidity because is effectively pulling in moisture from the earth.
Many homeowners will set cardboard boxes right on the floor or up against the walls. This does not allow moisture coming from the floor and walls to evaporate. Cardboard boxes will tend to trap moisture and become an ideal location for mold growth.
Instead of cardboard boxes, consider an alternative material that is not cellulose based to store your belongings in. It is also helpful to not store boxes directly on the ground or up against the wall.