I bought two of these. One is in my weather sealed gun safe, and one is in my closet next to my shower, keeping my shotgun dry. Before I had these, I would get light amounts of rust on my shotgun where scuffs and scratches existed on the gun. Even if I oiled them, eventually it would start rusting again. Now with the dehumidifier, there is no rust at all. Every couple months I have to plug in the device, but that is a very small price to pay.
I had a similar story in my safe, some of my rifles and handguns would get rust in places, and since I put in the dehumidifier, there is none. With the small area that is being dehumidified in the safe, and because of the weather seal, I only have to plug in the dehumidifier ever six months or so!