We use the "Damp Rid" bags you can buy from hardware / Walmart stores and hang them in the camper. This year we are trying a larger "bucket" this year. I put out Bounce dryer sheets (which I think also collect moisture) and Irish Spring soap throughout the camper. I would not put moth balls anywhere "inside" a camper - once that smell gets in, it is very difficult to get it out. I do put mothballs on the ground outside the camper around anything touching the ground, which for me are the tires and front jack. So far no mice after 10 years, the camper smells nice in the spring, and moisture / mold has been minimal.