I would be careful using them at all. Once I had one short out when I first started keeping Emeralds but luckly it was in a tupperware that was closed off with "air holes" for the mist to escape. Best bet is to get a large dish and place an aquarium pump and airstone. Even if the water dries out it will not heat up and short out. Foggers if they run dry on water can and in my case will burn out and possibly short. IMHO stay away from them.