A desiccant box fan is a DIY or purpose-built device, often for 3D printing, that uses a fan to move air through a box containing a desiccant material to remove moisture. This is more effective than a static desiccant box because the forced airflow helps dry filaments that have absorbed moisture and maintain low humidity levels. You can build one by attaching a small fan to a container filled with desiccant beads, or buy a pre-made filament dryer that incorporates a fan and heater.