I place 2, 4lb containers of Damp Rid in my boat each winter before the tarps go on for the outdoor winter storage. When I uncover the boat (32ft) in the late spring, the interior is dry, smells fresh and mildew free. Before I discovered Damp Rid, I would be cleaning some mildew out of the boat each year...no matter how waterproof the covers were. I don't have the luxury of indoor storage so this is the next best thing.